The Most You Should Pay: A Simple Formula
Work backwards from the selling price to the highest buy cost that still meets your ROI target.
The formula
Maximum buy price = (selling price − fees) ÷ (1 + target ROI).
Example
Sells at $80, fees $23, target 30 percent: 57 ÷ 1.3 = about $43.85.
Why it helps
You can decide at the shelf in seconds, and you know how much room a price match would give.
Add a check
Also require a minimum dollar profit.