The problem is that companies are deceptive in their adverts (and in the US this is apparently just normal and accepted). A company's ability to put out an advert that says "we're honest, our adverts don't lie to you" doesn't solve this problem for obvious reasons.

As a T-Mobile customer, and not paid at all to endorse their services, I can assert that their adverts do not lie.

Verifying that you are what you claim is definitely not free.

What does this even mean?

That there's still no magical way to know for free which companies are honest about their pricing and which aren't, in the absence of regulation. You can claim that you're just a happy customer and not a paid astroturfer, but it's not easy for me to practically confirm that (again, assuming there's no regulation to stop people falsely claiming those things).