My complete set is priceless.
That said, there have been a couple sets for sale over the last few years listed in the classifieds and it seems that it is a difficult thing to get much out of. A lot of folks just want some specific issues, but as far as the whole group of them, it is difficult to get what I would consider a good price for them as a whole. Probably the best way to get a good return on them is to sell them in lots of a year of two at a time on the auction site.
But you never know, you may meet up with the right person that appreciates them and is will to pay a fair price for them.
Most in good condition should sell for a couple bucks a piece, but there are 3 or 4 that are really hard to find that can be worth a great deal by themselves.