Only 2 unique sellers on OP right now, I'll mostly be relying on past confirmable sales.

http://www.tf2outpost.com/trade/12078113 Sold for sulphrous honcho+sweets worth a few keys, ~4.9

http://www.tf2outpost.com/trade/12020486 Sold for Blizzard TC, ~4.5 buds.

http://www.tf2outpost.com/trade/11873299 Bought for Bubbles TC + Bubbles Luchadore, ~3.65 + 1.05 = ~4.7

Seems a bit low for this hat, but hey, maybe hype for robo effects is finally dying down, and 3 sales in a .5 bud range usually isn't wrong. As for the currently open trades, they're all relists by the same 2 people, and don't have any significant offers, especially since the OP is looking for absurd prices like 8 buds in some of them.