There often is only a narrow range where (data + overhead) is larger than cache, but (data + 0) is smaller than cache. Cached reads/writes arent't free either,

There often is only a narrow range where (data + overhead) is larger than cache, but (data + 0) is smaller than cache. Cached reads/writes arent't free either, so if overhead drastically reduces those, you may come out on top 100% of the time.