Cypress is an unusual wood. Probably as expensive as cherry, and your vanity wouldn't be out of line at that price in cherry for custom work.

I only got one quote for a custom vanity, 54" wide, paint-grade, and it was about $650 from someone with no reputation. Your job sounds very custom, so it doesn't seem like a crazy price if this is someone you know does good work.

That sounds about right, I'd say. I had a very similar quote by a no name for a 56" vanity like kmcg. So, I've budgeted about 1k installed price for each of my vanity cabinets in my upcoming remodel.