A bank runs a "$300 when you open a checking account" promotion. Marketing celebrates: 10,000 new accounts in a quarter. Finance sees something else: $3 million out the door before a single dollar of profit arrives. Who is right?
Both, and neither. The answer depends on math almost nobody in the marketing meeting has done: the true cost to acquire each account against the multi-year value that account throws off. Get this wrong and you scale a channel that loses money on every customer. Get it right and you find the channels that quietly compound.
CAC (Customer Acquisition Cost): the fully loaded cost to land one new customer. Not just the ad spend. The bonus, the media, the agency fees, the onboarding, and the fraud losses from bad-actor sign-ups.
LTV (Lifetime Value): the profit a customer generates over their relationship, discounted to today's dollars.
The rule of thumb from consumer businesses is an LTVLTVLifetime Value: the total revenue (or profit) a customer generates throughout their entire relationship with your business.Voir la définition complète → to ratio of at least 3 to 1. Banking breaks the simple version of this rule because deposit and lending profit is strange: it is spread over years, it depends on interest rates you do not control, and a big chunk of your "customers" are only there for the bonus.
Start with the checking promotion. The headline cost is the $300 bonus. That is the floor, not the number.
Add the rest:
So a "$300 offer" might carry a true CACCACCustomer Acquisition Cost (CAC) is the total sales and marketing spend divided by the number of new customers gained in a period. It measures how efficiently you grow.Voir la définition complète → of $450 to $550 per funded, qualified account. That is your denominator.
Deposit accounts make money in ways that are invisible on a fee statement.
This is the engine. The bank takes your deposit and either lends it out or parks it. The spread between what it earns and what it pays you is NIM (Net Interest Margin).
A checking account with an average balance of $5,000 that the bank funds at a spread of roughly 2 to 3 percent generates something like $100 to $150 a year in net interest income. Modest. But it recurs, and checking balances are "sticky," meaning customers rarely move them.
The FDIC quarterly banking profile publishes industry NIM trends if you want to calibrate your spread assumptions.
Interchange is the fee a merchant's bank pays your bank when the customer swipes their debit card. For most banks it runs a fraction of a percent per transaction. An active debit user spending $1,500 a month can generate tens of dollars a year in interchange.
Note the regulatory catch: under the Durbin Amendment, banks above $10 billion in assets face capped debit interchange. Below that threshold, interchange per swipe is meaningfully higher. Your LTVLTVLifetime Value: the total revenue (or profit) a customer generates throughout their entire relationship with your business.Voir la définition complète → math is literally different depending on your bank's size.
A checking customer with direct deposit is your best prospect for a savings account, a card, a mortgage, an auto loan. This cross-sell value is often the largest LTVLTVLifetime Value: the total revenue (or profit) a customer generates throughout their entire relationship with your business.Voir la définition complète → component, and the easiest to overstate. Only count it if you actually convert it.
Now the deposit product that looks great and often is not: the high-yield savings account with a promotional rate.
A teaser rate is a temporary elevated APY (Annual Percentage Yield) designed to pull in deposits. The problem is the customer who arrives for the rate is, by definition, rate-sensitive. When the teaser expires or a competitor bids higher, that money leaves. This is hot money: deposits with no loyalty.
The marketing failure is measuring these campaigns on deposits raised, not deposits retained. If you spend to acquire $50 million in balances and $35 million walks within a year, you paid full CACCACCustomer Acquisition Cost (CAC) is the total sales and marketing spend divided by the number of new customers gained in a period. It measures how efficiently you grow.Voir la définition complète → for a one-year relationship. The LTVLTVLifetime Value: the total revenue (or profit) a customer generates throughout their entire relationship with your business.Voir la définition complète → collapses because there is no multi-year tail.
Rule: for teaser-driven deposits, model a decay curve, an assumption of what percentage stays each year, and discount accordingly. A retention assumption of 90 percent per year versus 60 percent per year swings LTVLTVLifetime Value: the total revenue (or profit) a customer generates throughout their entire relationship with your business.Voir la définition complète → enormously.
Here is the discipline. Compute CACCACCustomer Acquisition Cost (CAC) is the total sales and marketing spend divided by the number of new customers gained in a period. It measures how efficiently you grow.Voir la définition complète → and LTVLTVLifetime Value: the total revenue (or profit) a customer generates throughout their entire relationship with your business.Voir la définition complète → *per channel*, not blended. Blended numbers hide the losers.
| Channel | True CACCACCustomer Acquisition Cost (CAC) is the total sales and marketing spend divided by the number of new customers gained in a period. It measures how efficiently you grow.Voir la définition complète → | Deposit behavior | Verdict |
|---|---|---|---|
| Referral from existing customer | Low | High balances, sticky, cross-sells | Best payback |
| Branch / relationship opening | High | Sticky, strong cross-sell | Slow but durable |
| Paid search on "best checking bonus" | High | Bonus-seekers, high churn | Often loses money |
| Rate-comparison sites | Medium | Hot money, rate-sensitive | Payback only if retained |
The counterintuitive lesson: the cheapest bonus-driven channels often have the *worst* economics because they select for the least loyal customers. The expensive relationship channels can pay back better because they select for balance and tenure.
Vérification des acquis
1. When marketing celebrates 10,000 new accounts while finance sees $3 million in costs, what core concept explains why 'both are right and neither is right'?
2. Why does treating the $300 bonus as the complete cost to acquire a checking customer lead to a flawed CAC?
3. Why does banking 'break the simple version' of the standard LTV:CAC rule of thumb from consumer businesses?
4. Select ALL correct answers. Which costs belong in a fully loaded CAC for a deposit acquisition offer?
Sélectionnez toutes les réponses correctes.
5. Select ALL correct answers. What does 'bonus breakage' teach about interpreting acquisition economics?
Sélectionnez toutes les réponses correctes.
Ratio math (LTVLTVLifetime Value: the total revenue (or profit) a customer generates throughout their entire relationship with your business.Voir la définition complète → to CACCACCustomer Acquisition Cost (CAC) is the total sales and marketing spend divided by the number of new customers gained in a period. It measures how efficiently you grow.Voir la définition complète →) hides a cash problem. A 4 to 1 lifetime ratio is useless if it takes seven years to recover your $500 CACCACCustomer Acquisition Cost (CAC) is the total sales and marketing spend divided by the number of new customers gained in a period. It measures how efficiently you grow.Voir la définition complète →. You bleed cash the whole time, and you are betting on retention assumptions that far out are guesses.
So add payback period: how many months until cumulative profit per customer equals CACCACCustomer Acquisition Cost (CAC) is the total sales and marketing spend divided by the number of new customers gained in a period. It measures how efficiently you grow.Voir la définition complète →.
Walk the checking example:
That is slow. It only works if:
1. Retention is genuinely high (checking is stickier than savings, which helps).
2. Cross-sell is real and lands early.
3. You are not re-paying acquisition costs through churn and re-acquisition.
For a bank above the Durbin threshold with capped interchange, that same account pays back even slower. The economics are not universal. They are specific to your product, your asset size, and your rate environment.
The lens shift: marketing in banking is not campaign management, it is portfolio economics.
The Consumer Financial Protection Bureau's guidance on deposit account terms and disclosures is worth knowing, since bonus conditions and rate changes are regulated and misdisclosure is a real legal risk. Marketing does not get to invent terms the compliance team has not cleared.