Bandwidth, tasks and connections at once
Bandwidth has no cap. The limit is how many connections one address holds at once.
None of our packages charges per gigabyte or cuts bandwidth at the end of the month. What runs out first is the destination patience: many connections at once, leaving from the same address, get a slower answer or a block.
What to measure
Measure the response time with one connection, then five, then ten, on the same address and against the real site. The point where the time doubles is the practical limit for that destination, and it changes from site to site.
When the limit arrives, the way out is more addresses, not more bandwidth. That is why the package grows in quantity.