These aren't going for 3.5 keys anymore, certainly not 4.

Unsold 3.5

http://www.tf2outpost.com/trade/9682055

http://www.tf2outpost.com/trade/9763470 (With parts)

http://www.tf2outpost.com/trade/9696933

http://www.tf2outpost.com/trade/9487871

Unsold 3.25

http://www.tf2outpost.com/trade/9709494

Unsold 3

http://www.tf2outpost.com/trade/9776874

http://www.tf2outpost.com/trade/9778800 (My Own trade, I bought all three for 2.5 Keys)

http://www.tf2outpost.com/trade/9776600

http://www.tf2outpost.com/trade/9775964

http://backpack.tf/classifieds/search/strange%20widowmaker

One unsold for 3 Keys, four for 3.5, 2 for 3.75, and a ton for 4

Bought for 2.5

http://www.tf2outpost.com/trade/8632721

http://www.tf2outpost.com/trade/8619385

I'm leaving 3.25 in the range because I only found one seller at that price and as such don't have any proof against it. That and I believe this needs to have a range. Also, if you think I need more proof... well there isn't any. Even with 20 pages of sellers, most of them ask for 4 (not listed because there were simply too many) and above (some trades go up to 8 Key asking prices). Yes, some of the 3 key trades are rather new, but this isn't exactly a high-priced item, if 3 keys were as good of a deal as the current range suggests, so many sellers wouldn't be unsold (that and I closed my previous trade selling at 3 keys and opened a new one, the old one is currently a day old.)

Voice your opinions in the comments if you disagree with anything.