Another possibility in New Jersey is Rich Roman's company. I believe they are in the Newark area, judging from the area code, so not ungodly far from the Catskills.
https://www.trainlayouts.com/about/
Believe he built Mandy Patinkin's layout which is featured in one of the TM Video productions and has also been published in one of the magazines, as I recall.
https://www.imdb.com/title/tt0383969/
I've heard pricing closer to $300 per sq. ft. Second hand from a friend who spoke with TW TrainWorx (located in North Carolina and Texas, thus not in the Northeast, obviously). Likely it depends on scenery, complexity, etc.
Dunham has a terrific reputation if they are still in the layout construction business, and they are convenient to the Catskills. I had heard they might be retiring but check with them since their website is still active.
