The 29 key sale in the Headsplitter mini is an outlier (look at where current sellers still are), so it was closed: https://backpack.tf/suggestion/595fc999cf6c7535e627d5b2

Splitter mini: https://backpack.tf/profiles/76561198173728542#!/compare/1499558400/1499817600 - 18.5 pure

+

https://backpack.tf/profiles/76561198014269804#!/compare/1499385600/1499472000 - Added ~1 key of sweets (#81 Viewfinder) for Vivid Glengarry, mini at 24.5, 24.5 - 1 = 23.5

http://www.tf2outpost.com/trade/29263814 - B/O 21, caps there

Taking 19-21 for the Splitter.

Glengarry mini:

https://backpack.tf/profiles/76561197964171516#!/compare/1498176000/1498262400 - DBD Stove, ~27

http://www.tf2outpost.com/trade/29191386 - B/O 25, caps there

+

https://backpack.tf/profiles/76561198260967101#!/compare/1499299200/1499385600 - DP Pillar + 3.5, ~27

http://www.tf2outpost.com/trade/29244547 - B/O 24, caps there

Taking 24-25 for the Glengarry.

So the Splitter sale comes out to 28 overall.

Scrapprehensive has been selling one for 29 for 2/3 weeks.

New sale: https://backpack.tf/profiles/76561198101471399#!/compare/1499644800/1499731200 - Sold for duped Ghosts Swagman (needs mini, can't get one) and 2 pure

https://backpack.tf/item/4842300719 - Rotation

http://www.tf2outpost.com/trade/29251227 - B/O was 38

Other sales:

https://backpack.tf/profiles/76561198041219518#!/compare/1498521600/1498608000 - Auctioned for a Frostbite Buddy, ID#s match (~4 months old at 42)

http://www.tf2outpost.com/trade/29231061

https://backpack.tf/profiles/76561198134512931#!/compare/1498521600/1498608000 - Vivid Bandana, 40

Sales at 28, ~38?, 40, and 42, with a mature seller for 29. This is going to need a large range. I would trim 28 and 42 off and use the rest.