I ordered mine from Planet Aquariums. It was custom built and shipped to my LFS with their regular order so I didn't have to pay freight costs. I believe my 210g + stand + fitted lid + sump cost around $1500, and that was considered a really good deal several years ago. I would expect it to be like 25% more now. Definitely not the most cost-efficient route... but I sure got what I wanted quickly. That was low iron rimless glass - acrylic would probably run less.
I'd keep an eye on Facebook marketplace or your LFSs if they buy used tanks. If you're patient & in an urban area & lucky they occasionally pop up for ~$500-1000.
If you wanna go really big and are handy, plywood tanks are getting pretty popular now and there are lots of guides for building them online. I'm pretty sure I'll do that if I ever want anything bigger than my doorframe.