The one thing that disappoints me the most is that Neo Geo AES consoles still readily go for $200-$500 depending on condition and mods. I so want one of these but just can't justify the cost.
NES toploader - $40-$65 (too bad people can't see it's a piece of shit and exhibits the same annoying string of vertical lines as re-released computers from the 80's - unlike the original!)
The "dogbone" controllers that come with the top loader are much better than the rectangle ones that came with the toaster. Also the top loader doesn't suffer from the dirty/broken internal 72-pin connector problem. Most top loaders tend to go for $75-$100 on ebay depending on condition and included games.
This goes up to $150-$200 if the dreamcast has the broadband ethernet adapter (BBA). The keyboard and mouse generally add $30. The ultimate is the BBA with keyboard and mouse as the system will boot and run NetBSD and Linux.