You're assuming that processor power is still exponentially increasing. What if it isn't? Basic CPUs aren't getting much faster, ASICs are a one-time boost for performance by creating custom chips.
There's an ideology of Moore's law that assumes it's a given indefinitely, but just because it's been true for 50 years won't necessarily mean it's true for the next 50.
Not only that - memory isn't getting much faster either. If you need more memory bandwidth, you need more memory controllers, better NUMA access, more logic dedicated to keeping caches coherent and so on. In many applications, memory is the bottleneck and all that FP64 capacity will be begging for numbers to crunch.
Besides, not all problems are embarrassingly parallel.
Building huge compute clusters definitely provide an economies of scale, and can certainly reduce the cost of CPU, but it's a one-time fix. After a certain size, doubling the size of your datacenter doesn't have much if any reduction in cost.
Large modern data-centers have certainly added a few years to Moore's law as far as perceived performance, but they will also run up against a wall. In fact, the very emergence of large data-centers (as well as the rise in popularity of ASICs) are likely a response to the slowing down of Moore's law.
There's an ideology of Moore's law that assumes it's a given indefinitely, but just because it's been true for 50 years won't necessarily mean it's true for the next 50.