The concept of the Fediverse is horizontal rather than vertical growth - i.e. More smaller instances rather than increasing the capacity of the larger ones. We’re also seeing that Lemmy currently only scales to a certain degree. Right now, most instances are either covered by their admin because they’re so small that the cost is manageable or instances are setting up donations.
It’s conceivable that a business would set up an instance and charge for it - but I think it unlikely. A year town the road, though, who knows?