It sounds really worth it if I earned USD. Unfortunately I live in a place with a weaker currency and a strong immigrant population. I'll definitely subscribe once I try the teas they have around :)
What I've seen in some e-commerce shops is that they automatically change the currency based on the customer's location and have a small option on the bottom or top right of the site displaying available currencies. For your site a dropdown menu/box for the currency to the right of the price might be best.