Sale #1

Sold for 18 keys

http://backpack.tf/profiles/76561198090737788#!/compare/1465257600/1465516800

Sale #2

Bulk

http://backpack.tf/profiles/76561198019224682#!/compare/1463356800/1463443200

Sale #3

Quicksold for 13 keys to a quickbuyer

http://backpack.tf/profiles/76561198129731433#!/compare/1465689600/1465776000

http://imgur.com/QLtJQOJ

Sale #4

Should be used for Modest

http://backpack.tf/profiles/76561198051830317#!/compare/1465603200/1465689600

Sale #5

Sold for 12 keys

http://backpack.tf/profiles/76561198051830317#!/compare/1463356800/1463529600

Buyer counters

Sale #6

Sold for 10 keys

http://backpack.tf/profiles/76561198081963512#!/compare/1463011200/1463097600

Buyer counters

Seller at 16

http://imgur.com/IyUXmFQ

Conclusion

This clearly can't be 18 flat, given all the lower sales. Those sales only took a couple of days and since those sales happened there is now a buyer at 13, which should counter them. So instead I'm using a kinda young seller at 16 for the low-end