I was just wondering what I should do with my Feltrite?

I haven't sold any yet cause $25 seems like such a rip off. Is there something I can use it for later in the game? or perhaps an NPC who hoards feltrite and pays more than the going rate of $25?

One guy trades 20 for something another 50. You need to save 70 total. That's what I've read in the strategy guide and heard from another player so far.