영주권 변호사 비용 계약이후 일방적 변경 가능한가요?

It can’t be only $1500 for 3 people even if it was 2019.
I guess $1500 is only for the primary applicant (and is now $2000).
Btw, I-485 is not hard at all, and you may try it by yourself to save money.