I'm not even remotely convinced that it's a sufficient motivation. You would have to show that the long-term income from these medications (whose use is only potential) would exceed that of the long-term use of the cancer treatment (whose purchase is now all but guaranteed).
Imagine a gameshow host saying this:
"You have ten thousand dollars guaranteed, if you open door number 2 you will lose this, but there is an undisclosed sum there - up to about ten thousand and one dollars, though it could be nothing".
Would you open the door ? Because no smart businessman would...
For it to make sense the potential amount behind that door would have to exceed the guaranteed money by a massive margin, indeed so MUCH of a margin that the patients for whom door number 2 ends up containing 0 dollars could be paid off and you STILL make more than you would have made selling treatments to all the patients for life.