With DSL (given the slow speeds quoted here it would be DSL), the deal is that you pay a fixed price for DSL service, which theoretically will go up to ~24Mbps for ADSL2+ or ~90Mbps for VDSL, but it will degrade to lower speeds depending on the conditions of the wiring. Conveniently this removes any incentive for the ISP to improve the quality of said wiring, and even more conveniently is that you can't determine said quality without signing up to a plan (you can't just connect a modem on a disconnected line - it needs something on the other end, and while it would be trivial for the far-end equipment to allow any modem to connect and sync, it would remove said convenience, so it's not done).

I have yet to see a DSL plan whose price scales with the real-world modem sync speed or where you can find out with 100% reliability what kind of speed you would actually be getting.