Hasn't been updated in a little while. 1 key doesn't seem all that possible, being conservative nonetheless. 10 pages on outpost.

http://backpack.tf/stats/Unique/Merc%27s%20Mohawk/Tradable/Craftable

2x 7 ref

1x 7.33 ref

1x 7.77 ref

2x 8 ref

4x 1 key

Sellers below 1 key:

http://www.tf2outpost.com/trade/22541547 - 7 ref

http://www.tf2outpost.com/trade/22537914 - 7 ref

http://www.tf2outpost.com/trade/22575885 - 7.33 (not counting it as valid as it's too young, but worth keeping an eye on)

http://www.tf2outpost.com/trade/22536690 - 7.33

http://www.tf2outpost.com/trade/22552710 - 1 key minus 1 ref (he's adding a ref to the mohawk for a key)

http://www.tf2outpost.com/trade/22463924 - asking for 1 key or 7.44 ref, surprised 7.44 hasn't been taken

http://www.tf2outpost.com/trade/22530971 - 7.55

http://www.tf2outpost.com/trade/22513211 - 1 key or 7.88 ref

http://www.tf2outpost.com/trade/22517528 - 1 key + .33 or 8.11

Unsolds @ or above 1 key:

http://www.tf2outpost.com/trade/22551105 - 1 day

http://www.tf2outpost.com/trade/22551200 - 1 day

http://www.tf2outpost.com/trade/22553923 - 1 day (possibly sold one also?)

http://www.tf2outpost.com/trade/22559052 - 1 day

http://www.tf2outpost.com/trade/22540498 - 2 days

http://www.tf2outpost.com/trade/22533800 - 2 days

http://www.tf2outpost.com/trade/22529019 - bp.tf prices, 3 days

http://www.tf2outpost.com/trade/22522792 - 3 days

http://www.tf2outpost.com/trade/22517005 - 3 days

http://www.tf2outpost.com/trade/22518582 - 3 days

http://www.tf2outpost.com/trade/22529618 - 3 days

http://www.tf2outpost.com/trade/22495353 - bp.tf prices, 4 days

http://www.tf2outpost.com/trade/22484663 - 5 days

http://www.tf2outpost.com/trade/22475845 - 5 days

http://www.tf2outpost.com/trade/22488528 - "bp prices" 5 days

http://www.tf2outpost.com/trade/22378578 - 1 week

http://www.tf2outpost.com/trade/22408097 - 1 week

http://www.tf2outpost.com/trade/22511248 - 1 week

http://www.tf2outpost.com/trade/22425632 - 1 week

http://www.tf2outpost.com/trade/22411843 - 1 week

http://www.tf2outpost.com/trade/22412510 - 1 week

http://www.tf2outpost.com/trade/22182988 - 2 weeks

http://www.tf2outpost.com/trade/22157643 - 2 weeks

http://www.tf2outpost.com/trade/22155519 - 3 weeks

http://www.tf2outpost.com/trade/22047767- 3 weeks

Keeping it conservative as there is very little proof for the low end for there to be a flat value (I'll also be scanning for sellers every day and adding when necessary), taking 7 ref to 1 key, as there is just as much proof for 7 as 7.33. Counter suggestions / feedback are welcome.

7 / 8.16 (mid value of keys) = ~0.85, just to show proof of range.