Break-even script misses the zero point it claims to find in bank API pricing

A payments engineer published a short script to test how bank open banking access fees would affect a merchant's margin. The script's fee range stops at 10p, so every row stays positive and never shows the break-even point it is meant to find. The author argues break-even is simply the per-payment revenue minus other costs, independent of volume. Hidden denominators such as per-call billing, incomplete payment rates and fixed monthly costs can shift the result, sometimes flipping its sign. The analysis concludes that a model's cost assumptions, more than its volume assumptions, determine where the margin cliff falls.