Yes, Post Pay Counter supports caching and is compatible with WordPress caching plugins.
Post Pay Counter mostly implements caching for plugin settings, user settings and active payment criteria.
Performance gain of caching
With latest releases of Post Pay Counter and its addons, server side caching improves stats significantly. We will update this page shortly with new results!
Under normal conditions, the presence of server-side caching does not seem to affect much stats page load time. I have run a couple tests, loading around 10k posts with only the Post Pay Counter plugin active, both with memcached active and not. From the total time cost figure at the bottom of the following screenshots, we see that there is not much of a difference: