In a marketing context it never meant that, same as "satisfaction guaranteed" doesn't mean what you expect. It really means "product has a fixed price with vendor defined service level" vs "defined service level and variable price according to usage". "Unmetered" might be a reasonable shorthand.

Oh, it's totally metered.

Now it means “caveat emptor.”

That's true and practically every statement made in an ad aimed at the general public should be taken with just as many buckets full of salt grains.

If an ad for a lab oscilloscope were made that way, nobody would ever buy it.