If you are a serious collector and this is something you would enjoy both playing, and having as a conversation piece, I say go for it. A fair price is whatever you feel comfortable with paying. A lot of the time, game collecting is like collecting art. It's all about what you're willing to pay for the art. Basquiat is a good example. He was a Neo-expressionist painter from the 80s and his art looked like something a 6 year old would doodle on the wall in crayon, but one of his paintings sold for $110 million.
It's all about what you're willing and able to pay for something.