Proof below.

Sales:

http://www.tf2outpost.com/trade/15545419

-wanted 6 buds

-brigade+10 key sweets bought c9 pyromancer: http://www.tf2outpost.com/trade/14367372

-~4.9 buds, no overpay as offered

http://www.tf2outpost.com/trade/14336388

-wanted 4.5 buds

-sold for lantern merry+24 keys in the end=~4.5 buds, even if he added more the sale would still be counted as 4.5 max due to b/o

http://www.tf2outpost.com/trade/14337974

-a little old sale

-bought stormy bomber: http://www.tf2outpost.com/trade/13965407

-4.3 buds, no overpay as offered

http://www.tf2outpost.com/trade/14273798

-b/o of 6 buds, old sale

-brigade+planets lucha sold for (unpriced) disco hoodie+18 keys

-lucha: http://www.tf2outpost.com/trade/14278432

Current trades:

http://www.tf2outpost.com/trade/15339732

-b/o of 6 buds, 1 month

http://www.tf2outpost.com/trade/15552769

-b/o of 6 buds, 2 weeks

http://www.tf2outpost.com/trade/14418231

-wants 6 buds, 2 months

http://www.tf2outpost.com/trade/13085824

-very old trade, no recent notable offers

As with new effects, not many good offers to go by so I'll just use sales to form the range. Unusual overpay and original prices used when necessary.