Breakeven CPA is the most you can pay to acquire a customer before the sale loses money. The formula is average order value multiplied by gross margin percent. An $80 order at 35% margin carries $28 of gross profit, so $28 is the ceiling on what the first sale can afford in acquisition cost.
If customers come back and buy again, you can justify paying above breakeven CPA on the first order. That is a lifetime-value decision, and it should be a deliberate one with the repeat-purchase math written down, not a hope.