I can't find a Minisforum 790S7 for anywhere near the price of the base model mac mini. I am seeing $459.00 USD and that is "BAREBONE (NO OS/RAM/SSD)" [1]. I am comparing this to the M4 Mac Mini base model, that does indeed come with an OS, RAM, and an SSD[2] at $499 USD.
[1] https://store.minisforum.com/products/minisforum-mini-itx-pc...
[2] https://www.apple.com/us-edu/shop/buy-mac/mac-mini/apple-m4-...