We don't know yet if their will be endless boosters. I bet Covid will end up like the flu, where a portion of the population (especially the older ones) will get a shot every year.

because every case of natural immunity is a lost vaccine customer

They are not, because natural immunity isn't a 100% safe way out. Look at the new Omicron variant. It spreads even under the previous infected.

A corporation like that can't afford to lose 60% of its business.

They can because they knew from the first day that this wouldn't go on forever. And they are now the leader in mRNA tech. This tech will not only be used for vaccines. It's one of the most promising medical developments in the last few decades. In ten to twenty years even the standard cancer treatment will be probably based on mRNA tech and Pfizer and Moderna will make billions and billions with it.