A price that looks profitable can fall short if you only counted the purchase cost. Decide which costs you want to cover per unit and use the same definition to compare products.
An example with numbers
You buy an item for $24, spend $2 on packaging and $4 on shipping that you pay. If you sell at $40, $10 is left, 25% of the price, before other expenses. Subtracting only the purchase, you would see 40%.
Try it with your numbers
Use $30 as the unit cost and $40 as the price. Identify which costs are left out so you read the result as the contribution per sale.
Example figures for learning purposes. They are not a recommendation and do not replace professional advice.