Paste the competitor pages selling the same product, add what the unit costs you, and see where your price should sit on the line.
Fill in your cost and at least one competitor URL, then hit Suggest a price. Every number that comes back is traceable to the arithmetic shown beside it.
margin = (price − fees − cost) ÷ price. Competitor prices are taken exactly as the page shows them, tax included or not, so enter your cost on the same basis. Prices are read from structured product data first and only guessed from raw text as a last resort — the Read from column tells you which, and anything marked currency guess deserves a look.