“It’s complicated” is the cop-out answer, but it’s also true. I’m currently working for an industrial-scale Bitcoin mining company, and their ROI is closer to 3%. But they’re at a scale where 3% is still looooots of money. My home mining is -infinity%, but I do it mostly for the learning experience. I’ve seen larger home miners make enough to pay their homestead’s utility costs by getting solar panels and batteries for free and old miners for cheap. From what I’m seeing the key is the same as any other business: keep costs low. Buying $10k miners and building a $1m facility to house them doesn’t pay. $0 solar panels and $200 miners might.