Sadly, I know of several barns where board is $1000./month or more, but those are top show barns.
However, we're also talking about Northern NJ, which some pretty pricey real estate so I imagine board is pretty expensive there
So I guess my question for the OP is, what does board at this facility usually cost? I can see a half lease being more than half board, if it includes shoing and worming or other incidentals, but to justify a half lease fee of $500.; board should be in the $700 - 850. range. Is this schoolie wearing special shoes or on a lot of supplements? Getting injected with Adequan or Legend?
Before you irrevocably sever your relationship with this trainer and barn, I would at least ask some questions. If anyone's offended by you asking why the fee is what it is, well, then, you do need to sever the relationship, so no harm done.
But it's entirely possible that fee reasonably covers half or a little more than half of this horse's expenses. You won't know unless you ask.