I think I just figured this out:
2006 Tour de France
GC prize: 450,000 euros;
Daily malliot jaune prime: 7,000 euros.
S-17 Prime: 200 euros
Floyd was in yellow for 5 days, so the total prize would have been 485,200 euros. At 10% interest (not unreasonable for a credit card level purchase) and given the current value of the dollar ($1.5562/euro as of June 1 2008) were looking right at about $900,000. One ninth of that (GC winners traditionally, if not by contract, share the prize money with their 9 person team) is right about $100k.
Like Deep Throat said: "Follow the money."