I just wanna point out that this may sound easier then it actually is.
Pricing to sell isn’t always easy because you have to price it to sell all while making it so that you actually make a profit.
When I am making a product via deriving of someone else I usually like to look at how much other people have priced what they made from deriving from said product; but with that said it is also important that you try to keep in mind the work you put into it.
Also, on a pricing note; some people tend to like “nice looking numbers” such as even numbers, etc. Also, keep in mind that the whole making something 999 instead of 1000(for example) may still work on many, but not in days many a buyer see right through that marketing strategy.