Any tool that lists magic items with the price is strictly more useful than ones that don't. So yes.
My personal opinion on it is to list the prices RAW, whatever the formula is. Or the range of prices. Rather than trying to homebrew some rules and use those in the site. I only say that because you seem very interested in making a useful tool moreso than useful rules and most people play the rules as they are in the book (generally). Or at least, there isn't really a rule that isn't in the books that a majority of players use.