Welp, 6 month old Unusual price that really needs an update. The high end of 18 doesn't seem existent anymore.

Classifieds:

http://backpack.tf/classifieds/search/id/52001029ba2536b758000001 - One seller at 16. Recently made.

Sellers:

http://www.tf2outpost.com/trade/13366844 - Same seller in classifieds selling for 16.

http://www.tf2outpost.com/trade/13330765 - Has an offer of 13, but owner rejected 12 before. Has no current C/O. 2 days old.

http://www.tf2outpost.com/trade/13378028 - Selling at 15 keys, probably a quicksell.

http://www.tf2outpost.com/trade/13378028 - Buying any Bonk Helm he can afford with a Nuts n Bolts Prussian + 3 keys. Don't know what to make of this.

http://www.tf2outpost.com/trade/11246841 - Has an offer of 12.

http://www.tf2outpost.com/trade/12495572 - Has a C/O of 14, and would take 16.

Sold:

http://www.tf2outpost.com/trade/13189967 - Don't know much about this deal, but he sold it in a bundle for $50 in Amazon cash, which I can assume is around $17 per Unusual and that's worth around ~10-11 keys per Unusual. If keys were $1.3 though, then it would make it around 13 keys.

http://www.tf2outpost.com/trade/13358170 - Sold for Payday 2 Career Criminal Edition ($50, which in Steam terms is about 21 keys? Idk. Edit: http://www.tf2outpost.com/trade/13375139 Selling CCE for 14 keys.)

Conclusion: Most people are now realizing that "discontinued" means nothing. I am slowly adding proof, so that's why this section is empty. If I find more proof that disproves my range, I will close this suggestion and remake it. If you find counterproof, please present it.