Discounted LTV and CAC payback in cash

Leo's investor slide says a family pays about 28,000 UAH in its first year and costs 4,000 to win, so "LTV is seven times CAC". The 28,000 is sales: most of it goes to the tutor the same month.

LTV (lifetime value) is the contribution margin a customer leaves over their life: sales minus the costs each sale brings. Never sales, never GMV.

CAC is acquisition spend ÷ customers it brought. In October 2025 Klasna spent 240,000 UAH on ads and won 60 families: CAC = 4,000 UAH.

The cohort took English 16-packs, so each lesson leaves 184.50. Over twelve months its contribution adds up to 499,810.50 UAH. Divide by all 60 families who started, including those who left:

499,810.50 ÷ 60 = 8,330.18 UAH per family, about 2.1 × CAC.

On sales it would be 2,709 lessons × 620 ÷ 60 = 27,993 UAH. The slip is dividing by the families still active at the end: that drops the leavers and inflates LTV.

The September contribution arrives a whole year after Klasna paid for the ads. Money that comes later is worth less today: Klasna could have used it meanwhile, and later money is less certain. So each month's contribution is discounted back to the month of acquisition.

Hanna uses 2% a month for growth spending (about 26.8% a year). Month k is divided by 1.02ᵏ; month 0 stays as it is.

Month 11 (September 2026): the cohort leaves 26,937 UAH, or 448.95 per family who started. Factor: 1.02¹¹ = 1.2434.

448.95 ÷ 1.2434 = 361.07 UAH in October 2025 money. A year of waiting takes almost a fifth off.

Add up all twelve discounted months and the 8,330.18 becomes a discounted LTV of 7,683.74 UAH, 646 less. LTV ÷ CAC = 7,683.74 ÷ 4,000 = 1.92.

The slips: multiplying by 1.02¹¹ instead of dividing, or using 11 × 2% = 22% as if the rate didn't compound.

"LTV should be three times CAC" is a rough habit some investors quote, not a rule of finance. On its own, LTV/CAC hides three things you need to judge a channel.

• The horizon. Klasna's 1.92 counts only twelve months. Families still active in September keep paying; a longer view would raise the ratio.
• The discounting. At 2% a month the twelve months shrink from 8,330.18 to 7,683.74. A ratio on undiscounted numbers looks better than it is.
• The time to get the money back. Two channels with the same ratio can pay back in 4 months or in 14. The second needs far more cash to fund.

So read the ratio together with payback and cash: the October families return their 4,000 in the fifth month, and Klasna has to carry the gap until then. Above 1, every family adds value over the horizon; the open questions are whether Klasna can fund the wait and whether the channel's CAC stays at 4,000 as spend grows.

The slip is to kill a channel because a ratio misses a target nobody derived.

Payback is the first month where the cumulative contribution per customer reaches CAC. To find it, add the months one by one and divide by all customers who started, the same 60 families as for LTV.

October 2025 cohort, cumulative contribution per family:

• month 0 (October): 71,955 ÷ 60 = 1,199.25;
• month 1: 2,235.53;
• month 2: 3,068.85;
• month 3 (January): 3,896.03, still short of 4,000;
• month 4 (February): + 802.58 = 4,698.60.

CAC is paid back in month 4, the fifth month of the cohort's life. Note the counting: month 0 is the first month, so "month 4" and "the fifth month" are the same thing.

Discounted at 2% a month, the total by February is 4,537.09, so payback stays in February. Over a few months, discounting barely matters; it bites on the long tail of LTV.

The slips: dividing by the active families of each month (which climbs faster and flatters payback), or calling month 4 "the fourth month".

Payback isn't only a date; it is an amount of money Klasna must carry until that date.

The 240,000 UAH of ads left Klasna in October 2025, all at once. The families then paid back through their lessons month by month. The cash still tied up in the cohort at each month end is:

cash tied up = CAC spend − cumulative contribution received.

• end of October: 240,000 − 71,955 = 168,045 UAH, the deepest point;
• end of January: 240,000 − 233,761.50 = 6,238.50 UAH;
• February adds 48,154.50 and the gap closes.

For one cohort that is manageable. But Klasna acquires a new cohort every month. Each one opens its own hole of about 168,000 in its first month and needs four months to fill it. Grow the monthly ad budget, and the holes get deeper while the old ones are still being filled. That is how fast growth eats cash, even when every cohort is profitable.

The slip is to count only the month of payback and forget the money needed to get there.

A customer slide mixes numbers that look alike but answer different questions. For the October 2025 cohort:

• 27,993 UAH: sales per family in 12 months. What families pay. Most of it leaves to tutors, so it says nothing about value.
• 8,330.18 UAH: 12-month contribution per family. What stays after tutors, fees and video, divided by all 60 families who started.
• 7,683.74 UAH: discounted LTV. The same contribution, each month divided by 1.02ᵏ, in October 2025 money.
• 4,000 UAH: CAC. 240,000 of ads ÷ 60 families.
• 4,698.60 UAH: cumulative contribution per family by February 2026. The first month it passes CAC, so payback comes in the fifth month.

The honest ratio is 7,683.74 ÷ 4,000 = 1.92, not 7. Leo's 7 divides sales by CAC.

When you read someone else's LTV, ask three questions: is it on contribution or on sales? Is it discounted? Over how many months? A smaller number that an investor can check is worth more than a big one that falls apart at the first question.

For the October families contribution and cash move together: they pay for packages up front, and Klasna pays tutors twice a month. So payback on contribution and payback in cash land in the same month.

That isn't true for every customer.

• Late payers push payback out. A Klasna for Teams client can have exactly the same LTV, yet it pays each invoice 30 to 60 days after the lessons, while tutors are paid on time and the CAC was spent up front. Its CAC payback in cash comes about two months later than its payback counted on contribution.
• Prepayment pulls payback in. A family that prepays a 32-lesson package hands Klasna cash before the lessons happen. Its cash line can cross CAC before the contribution line does.

So always ask on which dates money actually moves. The gap until cash payback is money the company must have in the bank. Two customers with the same LTV can need very different amounts of it. The slip is to assume payback on paper is payback in the bank.

Payback is the first month where cumulative cash from a customer reaches CAC. Picture two lines: a flat bar at CAC and a rising line of cumulative contribution. Shortening payback means either lowering the bar or making the line climb faster.

• A lower CAC. A cheaper channel or better conversion lowers the bar directly.
• More contribution early. The first months matter most. Keeping families is the strongest lever: the October cohort lost 9 of its 60 families after the first month (51 left), and every family kept adds to every later month.
• Being paid earlier. A prepaid 32-pack brings cash forward without changing LTV at all.

What doesn't help: a blanket discount lowers what each lesson leaves, so the line climbs more slowly; invoicing later moves cash backward; fixed costs like office rent don't belong to one customer's payback at all.

The slip is to treat "more sales" as the lever. Payback is about cumulative contribution in cash against CAC, and only these three things move it.