It doesn't sell at 1.5 keys, and it's possible to get at 1 key.

Selling:

Classifieds:

http://backpack.tf/classifieds/search/947/1/0 - 1 at 1.3 keys (1 key + 1.66 ref.)

Proof of the above: http://i.imgur.com/E4AkijO.png

Offers:

http://www.tf2outpost.com/trade/9453040 - 1 day old, offered 1 key, wants 1 key + 1 ref.

http://www.tf2outpost.com/trade/7582430 - Offered 1 key + 1 ref. not long ago

http://www.tf2outpost.com/trade/6705871 - Loads of 1 key offers, 1 5 ref. offer

1 key:

Bought mine at 1 key: http://i.imgur.com/Fn3u8AK.png

http://www.tf2outpost.com/trade/9479862 - 1 day old, has 1 add

1.25 keys:

http://www.tf2outpost.com/trade/9499166 - New, has a willing buyer

1.5 keys:

http://www.tf2outpost.com/trade/9440694 - 2 days old, offered 1 key

http://www.tf2outpost.com/trade/9091569 - 2 weeks old, retracted add

http://www.tf2outpost.com/trade/9493861 - Under 1 day old, only offer is 1 key

http://www.tf2outpost.com/trade/9412176 - 3 days old, offered 1 key by the same guy as above

http://www.tf2outpost.com/trade/9356636 - 6 days old, same offer as above

http://www.tf2outpost.com/trade/9498341 - New, no offers

http://www.tf2outpost.com/trade/9492663 - Under 1 day old, offered 1 key by the same guy as the other ones

Buying:

1 key:

http://www.tf2outpost.com/trade/8479544 - Lowest offer is 1 key + 1 ref.

1.5 keys:

http://www.tf2outpost.com/trade/9474964 - Closed, bought one really quick from what I can see, the outlier, and I also think that he was desperate

Also to the link above, trying to go for profit: http://www.tf2outpost.com/trade/9409529 - read the newest comment, trying to sell it first for 1 key + 4 ref. and then for 1 key + 3 ref, the offer is c/o'd

So this buyers trade was for profit I guess, a fail in my opinion, since it's getable at 1 key.

Conclusion:

Doesn't sell at 1.5 keys, and traders are willing to sell at 1 key and 1.25 keys.

Thanks for reading, all feedback is appreciated and have a nice one.