you could get the annual supply, then cancel your membership and get the membership refund. then repeat next year. Its within their rules.

Seems like quite a pain in the ass to save the equivalent of $7/month. If you value your time at all it's barely worth it.

The simpler variant of this is to obtain a gift certificate. They are required to let you spend it it, so you can get into the store that way. Bring cash, though -- they don't love that people do this, so they don't always take credit cards on these transactions.