Sold for 21 keys:

http://www.tf2outpost.com/trade/25622819

http://backpack.tf/profiles/76561198091135535?time=1430722800 (May 4th)

http://backpack.tf/profiles/76561198091135535?time=1430809200 (May 5th)

Going to call this an outlier.

[Sold with Circling TF Logo Industrial Festivizer (14) + Strange Specialized Killstreak Festive Sniper Rifle (15) + Professional Killstreak Festive Ambassador (4) ]for Skill Gotten Gains Taunt: Rancho Relaxo (60):

http://backpack.tf/profiles/76561198050933686?time=1431068400 (May 8th)

http://backpack.tf/profiles/76561198050933686?time=1431154800 (May 9th)

60 - 14 - 15 - 4 = 27 keys

Presumably offered.

Sold with Circling TF Logo Industrial Festivizer for Fountain of Delight Taunt: Oblooterated:

http://backpack.tf/profiles/76561198107256033?time=1430118000 (April 27th)

http://backpack.tf/profiles/76561198107256033?time=1430204400 (April 28th)

Sold for Strange Professional Killstreak Australium Wrench (40) + 3 keys:

http://backpack.tf/profiles/76561198107256033?time=1429772400 (April 23rd)

http://backpack.tf/profiles/76561198107256033?time=1429858800 (April 24th)

Buyout of 34 keys

http://www.tf2outpost.com/trade/25768004

Sold for Miami Nights Jumper's Jeepcap (16) + 15 keys:

http://backpack.tf/profiles/76561198065124166?time=1428908400 (April 13th)

http://backpack.tf/profiles/76561198065124166?time=1428994800 (April 14th)

16 * .9 + 15 = 29.4 keys

Rounded to 29 keys

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Professional Killstreak Festive Ambassador:

http://backpack.tf/vote/id/555468fcb98d88b22b8b45e2