I bought a perfectly good WORKING 90K mile 2.5L base engine for $1,800 (its in my race car right now) so selling a core for $2K was a pretty good deal for you.
Condition/damage generally isn't really relevant (as long as there are no gaping holes in the cases) because once something fails in a M96, then everything in the engine is suspect and the entire thing needs to come apart and be properly rebuilt and its very hard to know what can be kept vs what needs to be replaced without a full disassembly and inspection.
Typically, a Boxster core is $1,000-$1,500, but it can vary depending on seller, buyer, location, and how badly someone needs to buy it or sell it.