I think the parent talks about the relation between miss/hit, not the actual cost of a miss. In other words, if a piece of code took 100ms with 100% cache hit and 200ms with 0% hit but now it takes 20ms with 100% hit and 100ms with 0% hit, your code is 5 times slower with cache misses, when before it was only 2 times slower. Yeah, it's faster than before, but the relative cost in terms of your available performance has increased.

And I'd agree with that statement. I have been doing some heavy profiling lately and it's fun to see how good are modern processors at executing even non-optimal code if it's cache friendly. However, the moment it needs to hit L3 cache or further, the pipeline stalls and performance goes down the drain.