Hate to say it, but CGI eats horsepower. I use laptops these days (because until recently, the folks I work for made me use my passport a lot), but even at the gaming-laptop expense level, you can get a decent CG-capable portable computing device for a decent amount of cash. The one I'm typing on was a firebreather w/ an i7 9th-Gen, 32GB RAM, SSD disks (2.5TB total storage), 17" screen, and a GTX 1060 GPU onboard when I bought it 18 months ago (still is)... paid $1700 for it, which for what I got as a laptop, was a hell of a steal.

Desktops? I bet you could get refurb bits to replicate what I got in a desktop form factor for $400-$500 or so... just gotta know where to look (newegg, pricewatch, etc), and YouTube is chock full of videos to help you assemble it if you're not sure how.