$269 (+ $70-100 shipping) will get you a MACCHIATObin (+ a 4GB DIMM), a mini-ITX board with four A72 cores, PCIe and FOSS firmware (https://github.com/MarvellEmbeddedProcessors/edk2-open-platf... or even just mainline TianoCore) capable of running a graphics card before the OS (thanks to qemu).

https://www.solid-run.com/product/SRM8040S00D04GE008S00CH/

$300 for a tiny Kirin 970 board with 6GB RAM.

https://www.96boards.org/product/hikey970/

$1200 will get you a Developerbox, 24 A53 cores, also PCIe and FOSS firmware.

https://www.96boards.org/product/developerbox/

£2255 will get you a 32-core Ampere eMAG workstation

https://store.avantek.co.uk/ampere-emag-64bit-arm-workstatio...

You can also order a system from Ampere directly, no public prices but they might be offering 16-core systems for less.

https://developer.amperecomputing.com/resources/