" I'm assuming $3K on top of this quote for construction materials to compare to other quotes. "

Why would you assume $3k? You have all you materials picked out right? Get it priced so you know exactly what this should cost you.

The $3K is for dry wall, cement board, lumber, etc. Construction stuff, not the finishings like tile, vanity, countertops, toilet, tub, etc.

Have you gone to see his work at other places and talked to other home owners? That should be done before you ever contract with someone. It just might keep you from joining many of the others, we see on this forum, with shoddy workmanship.

I paid $40K for labor only for a master bath full gut/remodel back in 2014, in Los Angeles. Your quote doesn't seem out of line for NJ.

A well detailed quote is always a good start.