Especially if it's not the latest hardware, anything older than "latest" is a worthless scrap that some people try selling like if it's worth something. It's not.
~
Big mining companies struggle to get their ROI and have been mining at a loss for some time - reason they are replacing ASIC's for HPC and switching to AI training.
Hint: it's not only the kWh cost! the whole infrastructure costs a lot of money to maintain.
You just destroyed your own argument!
Private small miners don't have to care about infrastructure as you don't need the same thing for a 30kw draw as for a 400MW farm, and everything is pretty scalable from scratch when you're a small two fans fan and one room would be enough, you won't have rent, you won't have maintenance guys, you won't have an accountant to care about and pay.
You have dirt cheap energy or even free one, you're better than the best farm by exactly buying and running scrap.