Rakuten.com has them for $49.99 + free shipping at the moment.
There was a deal recently for one at TigerDirect.com that was $29.99 after a $30 rebate, plus shipping ($6). Besides that, there was a great deal for them around BF last year for $40.
Check Amazon Warehouse Deals as well, as controllers show up there all the time in varying conditions, from $35 - $45.