Start from economics, not markup
A fixed markup can fail when channel costs differ. Model the actual marketplace first, then test the price required for your target contribution margin.
Know your floor
Break-even price is the modeled floor where contribution reaches zero. A commercial selling price should normally sit above that floor by enough to support advertising, overhead and profit objectives.
Scenario test
Test normal price, discount price, higher return rate and higher ad cost before committing inventory or scaling campaigns.
Use the numbers
Educational guidance is most useful when paired with your own SKU economics. Run the same assumptions through the calculator, then compare marketplaces if channel selection is part of the decision.