Whether it's worth the money is something you'll have to answer. If you have a use for it, then $75 isn't bad for most any "ready to ride" bike. But as for that specific bike, there's no collectability, nothing special as far as I know about a '90's Schwinn Sidewinder, it's just a matter of how much you want it and will use it. If it were me, I'd look for a better deal on an old mountain bike if that's what you want.........The Sidewinder model name does go back to the very early days of mountain biking, here's an '82:
http://www.firstflightbikes.com/1982_sidewinder.htm