It’s an apples-to-oranges comparison, as mcbio noted. In addition to the fact that cancer consists of manifold diseases while HCV is only one, a second key distinction is that the business opportunity for HCV drugs to generate very large sales is short-lived.
Since few new patients are becoming infected with HCV, the pool of patients to be treated will be much smaller in 10 years than it is today. Hence, it makes perfect sense for there to be a big bolus of HCV drug candidates in the clinic right now, before the one-time window of opportunity closes.