Probably the biggest deals you'll find will be 80's solid state games. They're almost 40 years old and most are busted, but they are very popular with collectors because they look good and play well.
So, often I'll see them for $200-$500 but will sell to collectors for more after shopping them out. They are super cheap and easy to repair and they're well supported by the aftermarket.
So pretty much any SS Bally under $700 is a good deal.