I'm not sure about anyone else, but I've never bought mods out of the Mod Store. They seem WAY overpriced. Like college degree from Sanford Brown overpriced. (Google it if you don't get that). I have ...
I've bought several mods from the mod store. Much less frustrating than farming for weeks (including refreshes of cantina energy) just hoping to find that one 5 dot 30 speed arrow or 5 dot crit damage triangle. Not to mention giving up shard farming with that energy.
3k crystals, or even better, 3m credits, is more than worth it in my book.