I have zero idea why footprint spells are the most popular this year...

Kinda rough amassing enough proof to make a range, but I'm gonna try my best.

Insta-solds for 2 keys:

http://www.tf2outpost.com/trade/23357669

http://www.tf2outpost.com/trade/23356877

Sellers for 2.4-3 keys:

http://www.tf2outpost.com/trade/23357375 (2 keys, 4 ref)

http://www.tf2outpost.com/trade/23359067 (2 keys, 5 ref, very fresh)

http://www.tf2outpost.com/trade/23313919 (3 keys)

Solds for 2.4-3 keys:

http://www.tf2outpost.com/trade/23352668 (2 keys 4.88 ref... but did sell very fast)

http://www.tf2outpost.com/trade/23353056 (2 keys, 9 ref)

http://www.tf2outpost.com/trade/23351844 (3 keys)

http://www.tf2outpost.com/trade/23351348 (3 keys)

http://www.tf2outpost.com/trade/23351348 (3 keys)

http://www.tf2outpost.com/trade/23350254 (3 keys)

http://puu.sh/crBzK/e748855f7e.png - Classifieds at the time of the suggestion. One 2.1 key seller has already sold (insta-sell), while I assume the others remain.

http://steamcommunity.com/market/listings/440/Halloween%20Spell%3A%20Headless%20Horseshoes - Bottom SCM listings are at about 2 keys, 1 ref in the key equivalent, but recent sales have been higher, closer to 2.3 keys and up.

2.4-3 seems the likely bet, given all the sellers and solds at 3, but some having limited success for less.