Cryptics been doing the whole "sell costumes for real money" for a while now. I don't know why anyone thought STO would be different. Same company, same business model.
C-Store items are purely optional and are in no way required to play the game.
The folks who make C-Store items are artists, not programmers, and couldn't spend time running through code and picking out bugs anymore than a painter could be expected to inspect the building he's painting for building-code violations.
As for playtesting, thats what the Tribble server is for (sort of).
I know you're all frustrated with the bugs. But complaining doesn't help. Notify Cryptic of bugs you notice and sit tight. They're adding content and patches all the time and have long lists of fixes in the works.