Let's say you're the only one allowed to make these things, because of copyright and trademark law. Let's also say that charging $25 instead of $10 doesn't halve the number of units sold. Let's also say you want to make as much money as possible.
Prices are only indirectly based on what something is worth, and only if the invisible hand of the free market is having a good day. More directly, they're based on however much they can get away with charging.