Doh! Shoulda checked Snopes first:
"Honesty and truly I say, there's nothing special about pull tabs which makes them exchangeable for time on a dialysis machine. These bits of metal are worth nothing more than the ordinary recycle value of the aluminum they contain. Though rumor claims pull tabs are made of a special metal or have a "higher aluminum content" than the cans they accompany (thus accounting for their imagined greater value), there's nothing to this notion ? the tabs are made from the same material as the cans.
A million pull tabs have a recycle value of just under $300 U.S. And that's before you factor in what it costs to collect, store, and transport them to a recycling center which will pay cash for them. When you consider the time and effort it takes to collect a million of anything, it's a wonder anyone would go to all that trouble for a mere $300. Far better to ask everyone you know for a penny in place of each pull tab they would have given you ? at least then when you were done done collecting your million, you'd have $10,000 to donate to your charity.
To put this in even clearer perspective, 100 pull tabs have a scrap metal value of 3¢."