Have a community/free/gratis version that can handle >= 16 cameras and it's usable (meaning not crazy restricted)
or
is paying, but not crazy scheme (like subscription etc..) So you pay once, and you can use that version forever for unlimited number of cameras.
It is strongly recommended to use a Google Coral. A $60 device will outperform $2000 CPU. Frigate should work with any supported Coral device from https://coral.ai
My bad I was thinking that coral was a SAASS... but anyway money goes to G*** so not the best...