Are you familiar with physical internet infrastructure pricing, or are you just assuming? I don't think access is priced as bandwidth. I used to work at a small business isp and that was not how physical access was priced, particularly over relatively bandwidth limited physical connections. Though perhaps you work in the industry?
It's going to differ around the world but in Australia for business connections I'm used to paying a separate fee for the physical connection (which will have a maximum throughput) and a separate fee for the bandwidth allocation and a third for the monthly data cap.
Australia is a bit of an outlier, mainly due to Telstra and the Gang of Four. I believe the polite expression for their actions is "maximizing shareholder value".