You are massively over estimating how much a copy of the entire history of ethereum costs.

You can store the entire blockchain on a 1 tb harddrive.

The cost prohibitive nature is only running an open rpc that you tell hundreds of thousands of people about. Then you will have to deal will letting all those people access that 1tb of data.

Quicknode lets you have a private rpc with the full history of the chain for dollars a month.