One of the best days I ever spent at a race track was in 1986 at Donington Park in England. It wasn't a race, or a test session but a day organized by Suzuki GB to sample their line-up for 1987.
By mid day I had sampled every bike Suzuki had to offer and inevitably had decided on my favorites. Three bikes stood out for me, mainly because I liked sports bikes: the GSXR750 and 1100, and the RG500.
Having raced 2-strokes for most of my time racing, I leaned toward the RG500 as my preferred bike of the line-up. This motorcycle engineering masterpiece had all of the best 2-stroke technology ever designed: disc valve induction, water cooled, expansion chambers, variable exhaust ports, etc., all of which added up to one high performance 2-stroke.
Today, the RG500s are highly sought after by collectors, and as such, it is almost impossible to estimate a price (how much are you willing to pay?). However, expect to pay around $15,000 for a pristine example.