For roughly 475 credits—again, the value varies—Microsoft will give you $5 to spend at Amazon, or Target, Burger King, Starbucks, or other merchants. Bing says

For roughly 475 credits—again, the value varies—Microsoft will give you $5 to spend at Amazon, or Target, Burger King, Starbucks, or other merchants. Bing says I have 25,130 credits, so about $264. I'll never know because I don't believe for a second it would be worth the effort to try and redeem them.