I would say that $650 is an okay price, not the greatest, and not a horrible price either. If you're in a hurry to own a P220ST, then buy it. If not, keep your eyes open for a better deal.
As clubster mentioned, keep your eyes open for a CPO P220ST. I know they're out there. I've seen them for sale. You can expect to pay less than $600 for those. Good luck on your search!