I guess the AHrefs case us a bit special...
They need to run queries from their own IP address space and using IPs from a cloud provider would get them banned...
The other option is to get their public iP space and have it announced by a cloud provider. So, in top of the VM pricing, there is some cloud and network engineering to do.
IPs is only part of their issues.
BIGGER is that managing huge datasets are expensive.