I looked into doing this with the AA cereal boxes a couple years ago. I figured the following math equation:
- 1,000 boxes of cereal @ $2/box (on sale at local store)= $2,000
- Donate boxes to local food bank for tax deduction (say $500 deduction). I had even called a local food bank and they confirmed they would take the boxes with the coupon cut, as long as the food was untouched
So for a $1,500 "purchase", I'd have enough miles for an international business class ticket (value $5,000-$8,000).
I even called Kellogg's (who's HQ I live about 2 hours from) to see if they would sell direct, which they would not).
Unfortunately, my wife was less than supportive, and reminded me of the time and opportunity cost of buying, cutting certs, filling out certs and storing 1,000 boxes.