I REALLY don't know why they accepted 5 flat

Proof:

Buyers:

http://www.tf2outpost.com/trade/14195145 - Bought for 4

http://www.tf2outpost.com/trade/13965054 - Has at least 1 willing seller at 4

Sellers:

http://www.tf2outpost.com/trade/14226399 - Selling for at least 4, the only offer in 2 days is 4

http://prntscr.com/1q0cbh - Sold for 4.8

http://www.tf2outpost.com/trade/14262093 - Selling for 4.66

http://prntscr.com/1q0buc - Sold for 4.5

http://bazaar.tf/trade/412235 - Selling for 4

http://www.tf2outpost.com/trade/14283857 - Selling for 4

http://www.tf2outpost.com/trade/14269344 - Selling for 4

http://www.tf2outpost.com/trade/14287438 - Selling for 4

http://www.tf2outpost.com/trade/14288189 - Selling for 4

http://prntscr.com/1q0cpb - Sold for 4

http://www.tf2outpost.com/trade/14217408 - Sold for 4

http://www.tf2outpost.com/trade/14230298 - Sold for 4

http://www.tf2outpost.com/trade/14245870 - Sold for 4

http://www.tf2outpost.com/trade/14253638 - Sold for 4

http://www.tf2outpost.com/trade/14215681 - Sold for 4

http://www.tf2outpost.com/trade/14283354 - Sold for 4 (he opened a trade at 4.5 and 4.33, both failed to sell, you can check his closed trades)

http://www.tf2outpost.com/trade/14255172 - Sold for 3.5

http://www.tf2outpost.com/trade/14257729 - Selling for 3

Classifieds had 3 selling for 4 at time of posting

Why I suggest 4 - 5 and not 4 - 4.5 or something? 5 flat was JUST ACCEPTED which is why many trades still sell for that much and it's probably possible, I suggest this because it's very simple to buy for less than 5, many sellers and the buyers that actually paid more than 3 keys bought already