D2C in Vietnam is in a good phase: easy to open channels, easy to run numbers, easy to create the feeling of growth. Which is exactly why so many brands don't know where they're losing money until the cash runs out. The question isn't "are my unit economics good," it's "at this stage, which number should I actually worry about."

Pre-PMF: don't optimize, measure honestly

The common mistake here is optimizing too early. You don't yet know who truly needs the product, but you're already worried about cutting CAC. The one thing worth measuring for real: does anyone buy a second time, and why. Without a real retention signal, every CAC/LTV number is a mirage, because you don't yet know what a customer is actually worth.

Post-PMF, scaling: watch CAC payback

This is when unit economics start deciding your fate. The first number I look at isn't LTV/CAC (easy to dress up), it's CAC payback: how long until a customer pays back the cost of acquiring them. If payback runs longer than your cash can hold, then the more you grow the closer you get to running out, even if on paper you're "gross-margin positive."

The warning threshold I use for Vietnam D2C: if payback runs past 4-6 months and you don't have long-dated capital, that's the moment to stop pouring into ads and look again, not to floor it.

Growing fast: beware pretty fake numbers

Three traps when the numbers are rising:

  • Blended CAC hides the bad channel. The average looks good, but one channel is bleeding, carried by organic. Split each channel out and you'll see where the blood is.
  • Repeat revenue is really repeat discounting. Customers come back for the discount, not because they love it. Kill the promo and they leave. That's not retention, it's bribery.
  • Inventory eats all your cash. Profit on the P&L, but the money is sitting in the warehouse. A brand that spikes then can't recover often dies from cash flow, not from losses.

A quick way to check yourself

You don't need to hire anyone to start. Sit down, split CAC by channel, compute payback for your biggest channel, and ask straight out: if I turn off every promo next month, how much revenue is left. Those three numbers are usually enough to know whether you're healthy or bleeding.

To look more systematically, I have a free D2C health diagnostic, 22 rules across 5 pillars, 10 minutes, no email needed. It won't replace a real conversation, but it's enough to see where things are breaking.