The money really isn't in the consoles, enough of them sold that they arn't huge collector items yet. Maybe in a few more years when people throw more away. At best your looking at 50 bucks for a NES in prime condition with 2 controlllers. Usually thats the price of a refurb unit thats garanteed to work.
The real money is in the games, some really rare ones will fetch a nice price, which ones do you have? I might even buy a couple off ya if you have some good ones.
Games usually range from 5-50 dollars depending on the game and the condition.