About 46,000 IHG/Holiday Inn points for about $50 in mailing supplies (MasterCard and tolerance for tedium required)
The deal- The 'Priceless Surprises' promotion between IHG and Mastercard gives you a game piece for each paid stay between November 15 and, I think March 1 or something. There's about a 98% chance that each game piece will generate a 500 point reward (value $3.50-$5.00) or better.
The 'hack' is that you're allowed to do up to 94 Alternate Method of Entry entries, which is mailing a 3x5 card to a Hello World PO Box in Kalamazoo, MI. And then they send your electronic game pice back to you after a few weeks (was supposed to be 5 business days, but the travel bloggers read the rules early and kind of crashed the system.
The Priceless Surprises web site:
Note that you must sign up for the IHG Rewards program and then additionally sign up for the Priceless Surprises promotion for this to work
Rules including AMOE instructions here- while preprinted envelopes seem to be okay, note that the entry cards themselves are supposed to be handwritten:
I'm supposed to get 13K oints in my account in a few days for the first 20 entries I mailed in around Thanksgiving