Well it's a single kilobyte, but 100 KB in aggregate.
It's almost entirely Google Analytics, unfortunately. Our ads are served from a different domain (4chan-ads.org) for specifically this reason (user privacy and cookie bloat).
So you never encountered any problems with the free usage tier and its limitations? Asking out of curiosity, as we use it as well and break the hit-limits every month. My direct supervisor asked me, if I envisioned problems, and I told him, Google does not guarantee, but delivers non the less (as far as I knew at that time).
How do you feel about the believability of the data?
Not saying you're doing anything wrong, just curious. I assume some of it is for ad tracking, but that's still a hell of a lot of data!