That for one, isn't about the devshttp://puu.sh/1Mfzl.jpg
This is it. Doing a simple division problem, you come out to needing 30,000 zombie kills to unlock a single skin, whereas to buy with GC it's a measly $2.75- I spend more than this every morning for breakfast.
At 14 hours in the game, I have roughly 400 zombie kills and ~15 player kills on my 'main' dudebro.
That's roughly 2 zombies per minute- usually in bunches.
Meaning roughly 15,000 minutes; at this rate, is needed to unlock a single skin of the 7 available. 250 hours of straight farming.
Say you ALWAYS got headshots, use an M4, and always buy stanag c-mags from the market.
C-mags are about $2, and contain 100 bullets. You would need 300 C-mags to get to 30000 kills, assuming you NEVER miss and NEVER lose any bullets and NEVER encounter other players.
Also, $FR_UNLOCK looks like a placement bit of code for an alpha state of a game. It just looks silly and unprofessional for something that should be 'complete'.