I'm not sure if this is a good deal or not. It's got an old Hayabusa motor with carbs and it doesn't run. Needs some fiberglass work too. I do know when these are running right, there aren't going to be many cars at any track day you attend that will be faster.
https://www.facebook.com/marketplace/item/344339198399237/
Looking over Radical's for sale section shows a few SR3s listed at a bit more than $25,000 USD, though there are few that are much closer $30,000 USD.
And, if it helps, we have a video on repairing fiberglass if you haven't seen it already:
I had seen that ad and I think it's a bit expensive given the fact that it doesn't run and needs cosmetic work.
Keep in mind that the suspension on these has a whole bunch of limited lifetime parts and if there is no record of them having been recently replaced, this could be a nice moneypit.