Proof below. Overpay calculated. Original prices used

Sales

http://www.tf2outpost.com/trade/15593792

http://backpack.tf/id/76561198038986052?time=1383984000 ---> http://backpack.tf/id/76561198038986052?time=1384070400

40 keys = 2.5 buds

Side note: Buds were 16 each at the time

http://backpack.tf/id/76561198017942224?time=1383811200 ---> http://backpack.tf/id/76561198017942224?time=1383897600

http://backpack.tf/id/76561198085806375?time=1383811200 ---> http://backpack.tf/id/76561198085806375?time=1383897600

Miami Guad, other guy added a Bubbling Grimm, a White Bills and some other sweets = 2.2 buds (outlier?)

http://backpack.tf/id/76561198085806375?time=1383724800 ---> http://backpack.tf/id/76561198085806375?time=1383811200

2 buds + 18 keys + S. Original = 3.4 buds

Side note: Taking buds as 16

Conclusion

Not sure which one's an outlier, but for the sake of conservativeness, Ill take the top two sales. Vote accordingly.

Help / Constructive Criticism / Additional Proof / Counter-Proof is ALWAYS welcome! >;3