There will never be a single cure for all cancers, but yes, people that invent or discover new medical procedures, drugs or whatever should be able to get as much money out of it as he or she can, just like any other industry. We do want medical advances to keep coming at the same speed right? If you limit the funds these people can make from their labor in time you will see less capital investment, fewer smart people doing the work and fewer new technologies.
If it means more to you to give everybody decent medical care than it is to advance medical science further for everybody, well, I guess that's your choice. It's an awfully shortsighted one, but a lot of left wing/statist positions are.
Except you aren't advancing medical science for everybody. You're advancing for the person that discovers it and the group of people that can afford it. You are no longer curing cancer.. you are simply allowing those that can afford it to live without it.
Only in the same way that DVD's and VCR's and Laser Disc players are "only for the rich". Eventually that sh**t trickles down. I'd rather have a cheap cure for cancer in 10 or 20 years and an expensive one in the mean time than no cure at all, ever.