Opinions are not proof.

http://forums.backpack.tf/index.php?/topic/7-how-to-create-a-good-unusual-price-suggestion/

There is one person selling for 18.5 on classifieds

generic "i think it should be this much" guy

http://www.tf2outpost.com/trade/9468941 buyout 18 keys, been up for 2 weeks

http://www.tf2outpost.com/trade/9946273 buyout 21 keys, been up for 20 hours

http://www.tf2outpost.com/trade/9913576 buyout 21 keys, been up for 2 days

http://www.tf2outpost.com/trade/9964117 here's OPs trade, no offers on it, only ~40minutes old

http://www.tf2outpost.com/trade/9894466 2 days, no offers

http://www.tf2outpost.com/trade/9955996 7 hours, "level 42 collectors item", no offers

http://backpack.tf/classifieds/search/399/5/35 18.5 keys right now

You have no proof, and you have no reason for a price change.... downvote