Here's the US ebay auction NES games $1 or even less or approx $2 - 3
http://www.ebay.com/sch/Games-/13997...14.l1514&_vc=1
Here's the Atari VCS section on ebay US:
http://www.ebay.com/sch/Games-/13997...Atari%25202600
Basically the same, lots of carts only for $1 or less, or $2 - 3.
Of course there's plenty more cheap NES carts on ebay than VCS, due to the amount of NES carts in the USA, so in the end there's also more dearer NES carts on ebay than VCSs.