I also just got a quote for 4k to fabricate and install - about the same as a large built in with the same company. We are going pre-fab instead.

I am a big fan of Costco for vanities. Currently there are 3 30in vanities on their site, 2 with marble tops.
https://www.homedepot.com/p/Vanity-Art-Ravenna-30-in-W-x-18-5-in-D-x-31-1-in-H-Bathroom-Vanity-in-Grey-with-Single-Basin-Top-in-White-Quartz-and-Mirror-VA3130G/306103059 - this is affordable and looks interesting, though vessel sinks are not for everyone.

I would look for something standard size, or go to a place like cabinet discounters and to find the doors/configuration that you want $4k is a lot.

That’s absurd. It’s a standard size. There is a stock vanity out there for you. What quality is so quirky that you can’t find it? We’ll shop for you!

A couple of years ago custom cabinets cost about $1000/LF (so $2500) and stone tops cost around $200/sq ft (so $800). With all the supply chain issues, I would guess that 4k would be a common quote.

A reasonable stock vanity and top will cost you $500, so you are essentially throwing $3500 away to have the draws you want and that your teen probably won't even care about.

I am renovating a small teen/guest bathroom, making it nice but not high end. To get my preferred mix of drawers and cabinet space, I have been advised to get a custom cabinet made. It will be about 30”w x 20” d. The quote is about $4k for the cabinet and stone top. It feels very expensive to me because the finished product will be a small, pretty basic looking vanity, but I know having anything custom made adds a lot! Is this a reasonable for such a piece in a mid range bathroom reno? (to be clear it is not that I think anyone is misquoting this, I guess I am more looking for advice as to whether this is an appropriate amount for a small basic vanity.) Thanks for advice.