ISPs like to offer, say $65 for service (without committing to a specific speed... Their 100/100 service is "up to 100Mbps" and not a guarantee.)
They then want to charge a modem rental fee - another $5/mo. They want to charge a wifi access point rental fee - another $5/mo. They want to charge various regulatory fees, universal access fees, taxes, etc. They want their advertisements to say "$65/mo", but they want to collect more like $90/mo.
You can buy your own modem and save that $5/mo (but they often push back against that, claiming your modem isn't compatible, or that other customers have complained about inferior service with that modem). You can use your own wifi AP and save that $5/mo (but again, they discourage it...) You can't get away from the regulatory fees.