coupon code: GMG20-GGN5D-FC3NA
Yes this has been on sale recently for the same price ($4.99) but it's lower if you use the 20% off coupon code.
This code was included in an e-mail from GMG and I don't see this coupon code on the GMG site like I usually do so I hope it's not a unique one for me.
If it is a single user code, someone comment and I'll expire my post. If you're a Steam gamer, it may be worth signing up for GMG's e-mails.