If you spent $5 on electricity but only get $3 of XMR you're losing $2 of XMR you could have bought on an exchange. That's is completely irrespective of owning a miner or not.
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If your goal is to make fiat money from crypto conversion, then it never makes sense to mine at a loss. NEVER.
I see your point and it is logically valid. Howerver, mining is almost never irrespective of owning a miner or not. It does make sense to simply buy from an exchange, but you may not be considering the factor that people who already have a miner, are already too invested to accept that they have lost. People who are mining at a loss are probably still in denial or are too lazy or passive to realize that they need to sell their equipment.
Yes I think it's logical to stop mining at losss. But selling the rig or not is another question.