If you can get it for $45 to $50 .... go for it. Don't look too anxious, just sincerely interested in it. $90 seems a little high. You know that $90 is the starting point...then add parts & your labor. It also needs to be cleaned up. Otherwise, real nice.

The thriftl store near me would probably charge $500 for the same bike

Of course they have good deals on sports jacket with cigarette burn holes in them