5.5 keys doesn't ever happen.

http://www.tf2outpost.com/trade/19376947 Selling 2 for 5 keys each

http://backpack.tf/classifieds/search/id/52cf1a3b4cd7b858118b4567 2 in classifieds for 5 keys each, one happens to be from the same guy as the last trade.

That's 3 on the market for 5 keys, I don't see a single 5.5 seller. All the other sellers are offers or failing to sell for like 7 keys.

...except for http://www.tf2outpost.com/trade/19365965 who is selling for 3 keys, but it's gifted. I'm not counting this as proof because gifted, but if anyone wants to snap a cheap chocolate bar up go for it!

Now if you'll excuse me, I have to go back into hiding from the amazon drones relentlessly hunting me down.