Because cacheex=3 is different way to sharing this thread is good for experience exchange.
Cacheex=3 make exchange in one way direction this mean that you send all your collected cache to your peer. Also you receive the cache in same way but in back direction.
The whole procedure continue all the time.
This sending and receiving cost us bandwidth. Quality cacheex is possible only if you have low ping and fast connection.
You are able to limit your bandwidth with tunning on Cache-EX Maxhop: values in account and reader section.
In account section that is compared to download.
In reader section is compared to upload.
In my case with maxhop = 4 in reader section and maxhop = 3 in account section and 25 exchanges I have 150 kbytes/sec download and 450 kbytes/sec upload traffic.