I found these two links interesting. There is a difference between Markup, which is what my formula calculates, vs Margin, which is what you were calculating with your formula. It’s an interesting read. Hopefully it translates well for you.
https://www.omnicalculator.com/finance/markup
https://www.omnicalculator.com/finance/margin
https://www.omnicalculator.com/finance/margin#margin-vs-markup