my isp says the usage is costing them big bucks to whom do they make the check out to?

ISP's act as gateways to the actual network. They run like any other business - with costs of staff salaries, equipment for installations, support, hardware, licensing, etc. These companies serve to connect houses to the actual cable network.

The physical copper wire in the ground and in the air, as well as fiber optics, are owned by a variety of other companies who have paid to have them laid. For example, in Southern Ontario, Bell owns the majority of the actual network infrastructure, and other companies will rent the use of some of the capacity.

In short, someone has to buy the cable, bury it, and hook you up to it. Add onto that a competitive industry where there are marketing costs, offices, staff, support call centers, and the like, and you get a pretty big bill. The payment starts with you as a user and is spread among a variety of companies, through your ISP.

It goes to equipment and maintenance costs. More users and higher bandwidth require better and more equipment such as switches and multiplexers. They also have to do line upgrades and such. It's frustrating, but somebody has to pay for all this