I bought a robot setup like this, no welding power source though, a few years ago for nothing, like $300 I think. Ready to rip, nothing wrong with it. I bought a 10lb capacity silicon wafer loading robot for $30 a little while back too. Todays market is pretty hot for used robots, but a few years ago it wasn't.
He could say he wants $500 or $50,000 for his robot setup and neither would surprise me. There's so much volatility today that you can find crazy deals regularly. One day I'll watch machines and tooling go for stupid money at auctions. Then 2 weeks later nice machines are selling for 1/10th of what I'd expect and I'm buying 1500 lbs of nice Cat40 stuff for 50 cents a toolholder. Wild times for sure.
OP should post a price. Saves everyone's time.