As for the lower plan being a poor value, that depends on your usage.

Might the poem itself then have become an authority on usage?

Some further examples can be found in the sections on usage above.

The type of road surface is dependent on economic factors and expected usage.

Windows Phone 7.8 however has increased battery life up to 10 hours on heavy usage.

If she meant no harm, research on American usage of words would have told her to choose a different term.

"We would guess that the people who cut down on their usage of red meat tried it and were satisfied."

You don't have tiers but rather charge simply based on usage at a given rate.

Extension activities section gives some information on American vocabulary and usage.

So which part you'll prefer will depend on your budget and intended usage.