Weird range, but proof is below. Still possible to buy for 1 ref, but people are willing to pay way more. Only 1.5 pages of sellers in the outpost.

Sellers:

http://www.tf2outpost.com/trade/13153514 - 1 ref, got a willing buyer

http://www.tf2outpost.com/trade/12780441 - sold for 1 ref

http://www.tf2outpost.com/trade/13186894 - willing to sell for 1 ref

http://www.tf2outpost.com/trade/13180322 - sold for a milkman (1.33-1.66 ref)

http://www.tf2outpost.com/trade/12913342 - 1.66 ref, 1 day unsold without bumps

http://www.tf2outpost.com/trade/12181025 - sold for 2.66 ref

http://www.tf2outpost.com/trade/12253841 - sold for 2.66 ref (check the items history)

http://www.tf2outpost.com/trade/13019841 - sold for 3 ref

http://www.tf2outpost.com/trade/12649678 - luger + summer shades (4-4.5 keys) + 2 wraps (2 keys) was sold for a vintage luger (7 keys). So the unique luger itself was 0.5-1 key (2.77-5.66 ref)

http://www.tf2outpost.com/trade/12028225 - offers 2 ref, 2.66 ref

http://www.tf2outpost.com/trade/12314871 - offers 2 ref, 2.66 ref (same guy)

http://www.tf2outpost.com/trade/11023707 - a lot of outdated offers (up to 1 key), fresh offer 2 ref

Buyers:

http://www.tf2outpost.com/trade/13223230 - 1 ref

http://www.tf2outpost.com/trade/13234442 - 1 ref

Also, trade.tf shows 1.88-2 ref - http://trade.tf/spreadsheet