It's not about selling kilowatts, it's about ensuring that your grid can deliver them to the customer.
In other words, you may well have to adjust the grid in an area to accommodate just one high-density user.
And who's going to pay for that adjustment? The energy company? His neighbors? Or the more-intense-than-average user?
If it concerned e.g. a bakery, you might amortise the changes to the grid over a ten-year period or so and charge them the standard tariff. Bakeries aren't very volatile.
But bitcoin mining operations are. They're decidely footloose, and they'll leave the instant their cost of moving shop is less than what they stand to gain from lower tariffs someplace else.. So there's a substantial risk they'll be gone next year if some other place decides it wants to sell off a bit of surplus power and undercuts your rates.
For that reason alone it's entirely reasonable to want to recoup the grid adjustment in a shorter period of time, through higher rates.
It's not about price-gouging bitcoin miners, it's about refusing to subsidise them with investment in free (for the customer) grid adjustments and risk not being able to recover.that investment.