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?
Yes! More BTC than you started with is a profit. Less BTC than you started with is a loss.
Exactly. It's incredible how is so difficult for some people to understand such simple concepts: You are buying a machine that mines bitcoins. If it mines less bitcoins than you have paid for it (or that you could have bought when you paid for the machine), then you did bad.
So I paid 7000USD for a Jupiter and if by any miracle I mine and sell BTC for 14000USD then I did bad?