"Is this a reasonable price?"
Yes, I'd say so. It has grips worth more than a hundred bucks. And to a collector.... as in most readers of this forum, S trumps N prefixes.
28's are headed north in price. Do a "completed auction" search on Gunbroker and look how NIB examples are bringing Mod 27 money.
Deals are still out there, I think you got a pretty good one.
GF