what I described above would be at layers 1 and 2 in the OSI model (the cable itself and underlying physical assets)
a company like Cogent, HE, they're providing at layer 3 the routers, network engineering, IP space (in many cases, not all, mostly for enterprise customers), and what is known as "IP transit" - transiting a customer's traffic through their network to all of their peers. And maintaining the cost of buying all those inter-city transport circuits to link all of their routers within their AS together.