Sale 1:

Sold with 1 key and 1 key of sweets for a Disco Beat Down Pom-Pommed Provocateur

(35*0.9) - 2 = 29.5 rounding to 30 keys

No outpost trade

http://backpack.tf/profiles/76561198127425902?time=1428735600 (April 11th)

http://backpack.tf/profiles/76561198127425902?time=1428822000 (April 12th)

Sale 2: (outlier)

Sold with 1.7 keys for a Miami Nights Hotrod

(19*0.9) - 1.7 = 15.4 rounding to 15 keys

{outpost trade link}

http://backpack.tf/profiles/76561198043732830?time=1427871600 (April 1st)

http://backpack.tf/profiles/76561198043732830?time=1428735600 (April 11th)

Notes:

http://www.tf2outpost.com/trade/25981093 B/O of 30 keys

Offer of 25.5 in unusuals, makes sale 2 an outlier.

Conclusion:

1 sale at 30 keys, an outlier at 15, and a B/O at 30 keys. Taking the final price at 30 keys.