I don't know how much time you have spent in NJ, so my advice and concerns would be first and foremost that. I assume you are coming ot NJ for work? Are you based in Princeton?
Use what ever advantages you have in negotiating as the motivation of seller and state of market will dictate the price you pay.
One has to know about what transpired between the township & how Toll aquired rights to building on this huge piece of land to understand the 'giving back' of land & the distribution of clustering for the developments built here by Toll Bros, sequentially.
The lots are very small for the single family & townhomes alike.
However, as the 'newest' Princeton Junction development , the advantages of being 3-5 mins from the train station & proximity to Rt 1 & shopping/amenities - it is very nicely situated.
The Mt. Vernon was built only on the larger lots--you may be paying for the premium paid by the 1st owner for the lot.
Price determination is made on several factors - Your agent should be able to work with you on that end.