taking a loss on the electricity he had invested to generate the bitcoins,
His marginal cost of generating bitcoins is probably close to zero. Maybe he owns a windmill and just pumps the electricity peaks, which would have gone to waste otherwise, into generating bitcoins. Same for the unused CPU cycles of his server farm.
This doesn't change the fact that selling bitcoins way below the market price would create opportunity costs for him. No rational person would sell a thing for less than people are people are prepared to pay it, even if they found that thing on the street.
Of course he might not be a rational person, but the majority of buyers will be.