The telcos/providers have always offered differing levels of service based on price.
Yes, and they can remain doing so with net neutrality. There's no reason for them to oppose this as they are already charging differing levels of service. Ending net-neutrality will actually allow them to double-dip on those "levels of service".
Competition between the telcos/providers has ensured the growth of the Internet and services to the public just fine,
Large swaths of the US are stuck with only one broadband provider. I still remember my dad suffering from Time Warner Cable's "only 1 PC per cablemodem" policy because it was either that or dialup.
any company trying to offer an unrealistically throttled service has simply lost customers as they went elsewhere.
Comcast didn't lose any clients over their lousy RST packet forging scheme. They stopped doing it not because their consumers got mad, but because the FCC gave them a slap on the wrist. Too bad the new FCC dude is a telco shill.