First Unusual suggestion, I tried ;=;

All of these were created within a month ago so no major economic changes with keys will change prices. It is the same brain bucket, keep in mind only 3 exist. I couldn't find any other Frostbite Brain Buckets other than the one right now. Not many exist therefore not many sold. This evidence is all I can work with.

Sold (sales?)

All of these trades are 1 month old, so it's very recent (and valid).

http://www.tf2outpost.com/trade/27841098

Got an offer of an unusual and a Max's head with spells. He asked for 70+ keys in unusuals/good items or 55 pure.

http://www.tf2outpost.com/trade/27835239

Asked for offers above 45 keys, and received a duped Sulphurous Ground Control

http://www.tf2outpost.com/trade/27724116

Again as previous trade they have asked for around 45 keys in unusual offers

http://www.tf2outpost.com/trade/27698918

Asked for 44 keys in pure, and 55+ keys in unusual offers.

http://www.tf2outpost.com/trade/27698918

Guy who named the thing we were following, rejected an offer of 34 keys. So we can assume it was too low of an offer.

http://www.tf2outpost.com/trade/27689509

Generally looking for offers, so we can infer that since 34 keys was too low and the guy wanted to make profit (most likely) it would have been higher than ~40 keys.

Current Sales

http://www.tf2outpost.com/trade/27900534

4 days old, bumped 17 hours ago at the time of this suggestion. No notes so they are open for offers, and previously as mentioned all others sold their unusual for around 40 keys. Last guy sold it for 70+ in offers so by following common sense and trying to make profit it would probably be the same as the last guy, maybe a bit higher.

http://bazaar.tf/profiles/76561198061108999

Same guy as above has made this Bazaar one 2 days ago at the time of this suggestion, and is asking for 50 keys.