Two definitive versions of Stern Spiderman. There are no differences in gameplay between any of them.

Spiderman Black (like a Limited Edition version you see with later titles) 400 produced. One run only. Value 8000-9000US. Maybe 10k in Aus. Anything over that doesn't sell.

Spiderman Red (Standard) - these had several production runs over the years.

Each run of REDs that Stern did they cut costs by removing generic components and replacing them with cheaper alternatives (a plastic apron instead of metal, plastic pegs to hold up the playfield instead of a metal support bracket et al).

However, just to confuse it a bit more they did a small last run of standard REDs for one of their 800 pound gorilla customers in the US in late 2010? and added custom webbed side rails. Some of the distributors in Australia piggybacked off this run and grabbed a few of them - the machine in the auction you linked to would be one of those mentioned with the custom siderails. There are no other major differences with this machine and a standard red besides the siderails.

At the risk of being called a tool since everything Stern does is apparently infallible - yes 6500 is overpriced. Anything over 6k for a standard red is overpriced unless it is NIB. That auction has been listed for months - I have had it in my watch list since Oct 2013 and it never sold over the Xmas buying spree. Somewhere in the mid 5 range would be more realistic if it had minimal time onsite in a commercial environment.

EDIT: The last run of standard REDs was $7k Australian NIB but keep in mind this was before the days of the cutback Pro models so it isn't really comparable to the Pro pricing now. It is more in line with a Premium model in terms of features.

Hope this helps.