Personally, I like the idea of C-Store and the points into it. I would say things are over-priced though.
Like, -Way- over priced. Either that or you need to offer more c-points for the buck.
Also, master keys need to be brought down. By a lot. Comparing to how often the lock boxes drop, and how many you can actually open, personally I'd say they need to drop 85% - 90% in price. Make the Master Keys 5 to 10 (15 tops) c-points to buy. 100 is just too much to try and be appropriate for how many lock boxes are dropping.
Also, while I just said most things are over-priced, maybe make a point of having the "special" ships that only appeared during special occasions in there by themselves at a higher price. Sure, the Jem'Hadar ship -could- have been gotten from something, but no one necessarily cares about the doffs you could get the ship from, they -just- wanted the ship. So maybe make the ship available for 2500 c-points.