If you use the original price for the drill it is 4 buds.

http://www.tf2outpost.com/trade/14178861 - sold with a steaming topi for a ss company man ~1.5 buds --> outlier (same guy as drills)

http://www.tf2outpost.com/trade/14592179 - sold 1:1 for an electrostatic aa? (no signs of sweets in their trades) - 3 buds

http://www.tf2outpost.com/trade/14768920 --> http://www.tf2outpost.com/trade/14822126 - sold with a n&b biccorne for a duped mn broadban (~4.5, maybe less) = ~leaves the bucket at ~3-3.5 or so.

http://www.tf2outpost.com/trade/14312951 - sold for ghosts softcap (not more than 3) + 1 bud

Your suggested range is fine, since the user who traded it for the drills had no clue what he is doing/doesn't care about profit.