Even if you just consider all of those 4000 + survivors would have got treatment for the cancer after getting it which costs far more than a vaccine.

Yep and significantly more than the death count would have needed expensive treatment and be out of the workforce for a time or permanently. Also the charged price isn't real cost to the economy. If they have a big margin on it after fixed research/approval expenses lots of it feeds back into the economy through taxes and dividends/reinvestment in other drug development.

Beyond death, it can also cause sterility and people may end up with extremely expensive IVF surrogacy pregnancies etc.