Sale 1:

Sold for 35 keys

http://www.tf2outpost.com/trade/28823138 - B/O of 35

Seller: http://backpack.tf/profiles/76561198014501079#!/compare/1489363200/1489449600

Buyer: http://backpack.tf/profiles/76561198154334102#!/compare/1489104000/1489449600

X = 35

Buyer’s end shows 32 keys, but 3 more keys were used to purchase the cotton head:

http://backpack.tf/profiles/76561198071167440#!/compare/1489363200/1489449600 (last 3 keys)

http://backpack.tf/item/5577030991

http://backpack.tf/item/4438085807

http://backpack.tf/item/4394641695

Sale 2:

Sold for 35 keys

http://www.tf2outpost.com/trade/28838489 - B/O of 38, buyer comments on trade.

Seller: http://backpack.tf/profiles/76561198154334102#!/compare/1490400000/1490659200

Buyer: http://backpack.tf/profiles/76561198076658566#!/compare/1490400000/1490486400

X = 35

Sale 3:

Sold for 33 keys in ~6 days

http://www.tf2outpost.com/trade/28791421 - B/O of 35

Seller: http://backpack.tf/profiles/76561198054067158#!/compare/1488067200/1488240000

Buyer: http://backpack.tf/profiles/76561198014501079#!/compare/1488153600/1488240000

X = 33

Sale 4:

Sold for 33 keys

No outpost

Seller: http://backpack.tf/profiles/76561198024410622#!/compare/1491350400/1491436800

Buyer: http://backpack.tf/profiles/76561198174172569#!/compare/1491350400/1491436800

X = 33

Sale 5:

Sold for Showstopper Buy a Life

Seller: http://backpack.tf/profiles/76561198174172569#!/compare/1491436800/1491523200

Buyer: http://backpack.tf/profiles/76561198066315540#!/compare/1491350400/1491523200

Should be used on the Buy a Life.

Sellers:

44 keys:

http://i.imgur.com/6gdGzZB.png - 3 months

http://backpack.tf/u/76561198018823628

http://www.tf2outpost.com/trade/28785025

45 keys:

http://i.imgur.com/m45waag.png

http://backpack.tf/u/76561198076658566

http://www.tf2outpost.com/trade/28848593 - 4 weeks

$100 USD (marketplace):

https://marketplace.tf/partneritem?sku=30182;5;u15&attrib=bp

http://backpack.tf/u/76561197966756586

http://backpack.tf/item/2503350802

http://www.tf2outpost.com/trade/28875391

Sales at:

33 (2x)

35 (2x)

Going with 33-35.