3 months old is pretty recent, but who doesn't love a fresh price?

Sale 1: http://backpack.tf/profiles/76561198050953597#!/compare/1491177600/1491609600

Sold for Midnight Whirlwind Disco Fever (27.5)+1 key + Tour of Duty Ticket (12 ref)

~29 keys

Sale 2: http://backpack.tf/profiles/76561198079578383#!/compare/1491523200/1491609600

Sold for a Duped Purple Confetti Engie Cap (15 keys) + Blizzardy Prancer's Pride (15 keys) + 1 key + Tour of Duty Ticket (~0.5 keys).

MINI: Only 1 seller for the Purple Confetti Engie Cap, and it's duped. http://prnt.sc/eubynn

~33 keys

Sale 3:

http://backpack.tf/profiles/76561198198392589#!/compare/1488585600/1488672000

Sold for a DBD Counterfeit Billycock (20.5)+ 2 keys pure + about 2.5 keys in sweets

=25 keys

Sale 4:

http://backpack.tf/profiles/76561198070773303#!/compare/1488499200/1488585600

Sold for Electrostatic Noir (*26 keys) + 1 key pure

*:MINI- Even though it was priced at 28 pure, there's a bumped seller at 26 who hasn't sold in 21 days. http://prnt.sc/euczvn

=27 keys

28 key seller: http://prnt.sc/eud7fb

25 key seller on Outpost, hasn't sold for a month. http://www.tf2outpost.com/trade/28818980

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TL;DR[

Sales at 29. 33, 25, 27 and sellers at 28 and 25.

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33 is an outlier as most sales happened in the mid-to-high 20s range, and it's hard to price the duped Engie's Cap at 15 with only 1 seller on the market (which is selling said dupe).

Going with a range of 25-29.