I just did a dummy booking and sure enough - there is was. The ability to double or triple the amount of miles you accumulate for a fee.
The caveat - The double or triple miles purchased will not count toward preferred status.
I think it's interesting that everyone is trying to sell miles right about now. How do FF's feel about this? I think I can see the appeal for infrequent travelers or those that need a boost for an upcoming award trip. Not sure I get it for everyone.
(But anyway you can make a dime is the name of the game