Here's my metric: I do complicated merges once in a while. If Beyond Compare (price = 60$) helps me resolve the conflicts in few minutes, of what used to take an hour of cursing and sweating, I pay them and consider the money well spent, because I can spend that hour (and a lot of others) that the tool freed up for me, earning money. The tool pays for itself basically.
If it's a niche market, low prices is rarely a viable approach because you won't have a lot of volume. Also, all the info you have about app stores and revenue are based on the total mass, or on the top-100 lists, and niche apps fall completely outside of it. There are actually a few narrow categories where you can get away with a high price.
And honestly, if you look at the app, a higher price would feel like a ripoff.