It's $300 at minimum, and usually more than $400. Of course "terribly expensive" is a relative measure, but I borrowed it from a discussion of the Odroid forum: https://forum.odroid.com/viewtopic.php?t=35941

Thanks for the info.

Udoo bolt v3 (3 GPU CU and 2 cores) is around $330 and the v8 (8 GPU CU and 4 cores) is around $420.

https://www.udoo.org/udoo-bolt/

Alternately, you could buy the Asrock 5x5 barebones kit.

https://www.tomshardware.com/news/asrock-am4-motherboard-ryz...