Of course its about the $ value
How would you feel about ROI on miner hardware if the reverse was true?
If you had paid 100 BTC for a miner when BTC was worth $100
You mined 101 BTC but BTC value dropped to $50
Would you say you have made a ROI? I'd say not.
Some people don't find trading BTC a satisfying vocation or even pasttime. Some people like to mine.
As far as hobbies go if my Jupiter makes as much as it cost me in $ and then some then I am happy enough and fuck what the wife thinks, at least I'm not pissing it away in the pub

People should have more respect for miners, for without them ROI or not there would be no BTC in the first place for people to trade. Let us have our fun without rubbing our noses in it.