system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is home internet data sold on speed and mobile data sold on amount used?
gpt
Capacity and oversubscription. When you get a physical wire connecting you to a network, that infrastructure is, on some level, adding additional capacity to the network you're riding on. More money, more cables, more bandwidth. With wireless transmission, however, everyone shares the same air. Improvements in transmission rate are purely a function of devising more sensitive, more expensive transmitters and receivers, which can produce a more granular digital signal. Where a 3G radio sends one bit of data, a 5g radio must send 400 bits, in order to cram more data over the same spectrum channel.

The upshot here is that while wireless infrastructure is relatively inexpensive to deploy, because last-mile costs don't exist, it's also organically much, much more contentious, and must be shared by anyone who happens to move into the range of a particular cell tower. So, mobile providers have chosen to price their services in such a way as to exert downward pressure on utilization, and the simplest way to do this is to establish a quota for users.

One other feature of a home or business internet connection is that it's always going to be in the same location. So, it's much, much easier for network planners to allocate resources to where demand is highest, in fact, a high concentration of high-bandwidth users is actually *less* expensive for an ISP to accommodate than a diffuse group of low-bandwidth users, because a strand of fiber-optic cable can carry a **TREMENDOUS* amount of data.