Yesterday I think.. You can keep an eye on the
Group Buys threads and see if anyone starts a new group for next happy hour on it. Seems it actually got as low as 1.17$.
It would certainly be nice. If I had the damn thing I would be non-stop testing with several games all damn day and posting the results to youtube, tinking with emulators, running benchmarks, etc,etc
http://steamcommunity.com/groups/groupbuys/discussions , where you can get almost any indiegala bundle they do when it reaches Happy Hour, with the prices often being lower than 1.5$ for the whole bundle.