I think the right way to think of it, from a self-protective perspective, is this: the real offer is the per-token pricing. Use that for a while, and iff you are consistently spending more than $20/mo, treat the subscription offering as a discount on some of that usage. So only on that condition, try the subscription and see if your monthly costs go down (because of the short term rate limits, they may not, depending on your usage patterns!).

But the opacity itself is a bit offensive to me. It feels shady somehow.