I talked with Gary last year about BTTF.
He said... not the good market as it scores only 2/3
1) young people, bar players: no
2) Collectors: yes
3) I buy only one pin in my life guys because of the theme: yes
I do think it could be selling enormous, but he has a point. It isn't an 'active' theme like metallica, the walking dead. But batman 66 isn't either.
So you never know.
I would sell a few games immediately to fund my purchase I'm afraid.