Looks like all the Halloween paints are jumping up in price fairly quick as stock runs out. I've collected every trade with a set price, and paints in stock on outpost. (Might of missed one or two) Tried to collect as much data as possible from the seller's (I was only able to contact a few) but here's what I found.

Average asking price on outpost - 15.6

Average selling price - 14-15 (As a consumer, I have personally bought one at 14, it was nearly impossible to find one for cheaper.)

Some trades

http://www.tf2outpost.com/trade/10267875 20 keys (Wasn't able to contact them)

http://www.tf2outpost.com/trade/9289886 16 keys (Sold 2 at 14, and sold one for an O.Fire Outdoorsman just upped the price, restocks often)

http://www.tf2outpost.com/trade/9382832 20 keys (Wasn't able to contact them)

http://www.tf2outpost.com/trade/8271995 18 keys (Says he sold a dozen at 14+)

http://www.tf2outpost.com/trade/8159380 15 keys (Last online 5 days ago, no contact)

http://www.tf2outpost.com/trade/10151594 14 keys (Wasn't able to get in contact left, has 2 left in stock though)

http://www.tf2outpost.com/trade/10288620 17 keys (19 days last login, no contact)

http://www.tf2outpost.com/trade/10400996 12 keys (Looks like someone bought it, not sure if they have more stock)

http://www.tf2outpost.com/trade/10205856 12 keys (Sold out)

http://www.tf2outpost.com/trade/10412081 12 keys (2 in stock, will most likely go fairly quick, that is if he even has them anymore.)