This is really cool. Have you thought of doing on-demand pricing? I'd send a few cards, but I don't want to pay $30 a month for a service I might only use intermittently.
Thankster.com can do this with on-demand projects or via our plans for integrations. We're very flexible. You can reach out via the site and if you can mention HN we'll give a discount on your first order.
Why is this not just
10 cards = $30
20 cards = $50
50 cards = $100 ?
Shady business tactics.