It costs a 100 coins.
Go here:
http://fgunz.net/donate
You get:
20 Coins for each USD using PayPal.
15 coins for each USD using Mollie.
10 coins for each USD using other methods
So paypal is the best. 5 bucks will get you the shotty.
Once you donate you become VIP, and get that title in game too. And then let me know, I'll send you the link to the red shotty =)