Time Machine would probably be the easiest to find in the US , Just a guess on price but somewhere in the range of $1,000 + or - depending on condition .
Pinball Champ my friend bought one a few years ago for $500 in decent condition but it was missing a lens insert in the playfield , Other wise nice .
Robot great game not so easy to find , around 7 years ago my friend got one for $1000 in nice condition , I would have no problem paying him $1600 for it today but he could probably get more and has no intention of selling it any time soon .
Farfalla could have bought one last year from a friend $1000 and it would have come with an extra (mostly populated ) playfield . I did buy just the playfield .
I bought a Devil riders from a friend not too long ago paid $200 but it needed quite a bit of work and had no backglass