This is a pretty old price, and needs updating.

Declined 1 key or more:

http://www.tf2outpost.com/trade/21646216 (Declined 1 key twice)

http://bazaar.tf/trade/722022 (Declined 1 key, 1 ref, and 1 key,

Buying. 1 key:

http://www.tf2outpost.com/trade/21426391 (3 weeks, 0 offers)

http://www.tf2outpost.com/trade/21552925 (2 weeks, 0 offers)

http://www.tf2outpost.com/trade/21450459 (2 weeks, 0 offers)

http://www.tf2outpost.com/trade/19528827 (3 monthes, but hasn't bought one in 2 monthes)

Buying Less than 1 key:

http://www.tf2outpost.com/trade/21751745 (5.66, 1 week, 0 offers)

http://www.tf2outpost.com/trade/19314787 (5 ref, 3 monthes, 1 offer 3 monthes ago)

http://www.tf2outpost.com/trade/21611644 (5 ref, 1 week, 0 offers)

Sellers:

http://www.tf2outpost.com/trade/21596301 (4 keys)

http://bazaar.tf/trade/768168 (1.5 keys, offered a Sub Zero Suit)

Sold on the Community Market:

http://steamcommunity.com/market/listings/440/Strange%20Leftover%20Trap

Unfortunately, I was unable to find a significant amount of sales on Outpost, so I turned to the market for an accurate recording of recent sales.

Outliers in the last month: High- 7.99 or 3.2 keys--------Low- 2.71 or 1.1 keys

Minus the two outliers above, the price of sales in the last month averages $4.60 or 1.84 keys out of 63 trades.

So, giving it a little leeway on both sides, I think that 1.5-2 keys is a fair price for this item.