Found this over at Slickdeals. I've already purchased 2400 points for $10+tax. Not sure how much longer it will work. All credit goes to akravator ar Slickdeals.
http://slickdeals.net/f/6050586-Xbox...0-Points-for-5
You'll have to search the thread for codes, but this one (XboxEMWAo73d7ehgn) worked twice for me.Xbox Live Microsoft 1200 Points for $5
The Microsoft Store is selling the 1200 points card for 14.99 - 10.00 (via code) = 4.99 + tax.
The $10 off code applies to the entire order so buying two cards at once costs 20. It can also be used on 1200+ points cards. Clearly, it is best to just buy one 1200 card at a time.
It took me about 15 minutes to get an email and the codes are available in the downloads section of your MS account profile.
1200 Points