I don’t think it works like that.

If you can find and patent a cure to cancer, you can charge whatever you want for it, at least in the US. I don’t think profit would be an issue.

And even if ending chemotherapy would discourage the incumbents, smaller companies would love the opportunity to kill them.

For example, Polaroid didn’t want to embrace digital cameras since they made tons of money selling physical film. But all the smaller camera companies didn’t care, since they weren’t benefiting from that and wanted to just take Polaroid’s market share. And that’s why digital cameras took off regardless.