I don't want to say "I'd buy this if you made this change" because I live on a farm, but I would be a LOT less price sensitive if the seeds were described in a manner that made them sound more special. (even if I didn't know the variety off-hand.) Kentucky Blue Pole Beans, not 'Beans' and Organic Red Velvet Okra, not 'Okra'.
I wasn't sure I understood how large of a garden each seed pack is supposed to service. When you say '3 10 foot beds' does that mean 30 linear feet, or 300 square feet?
I'd also make sure you get real-world feedback about the plans and the pricing. If I was you, I'd go talk to people at local garden centers, and I'd bring my iPad and I'd ask them for help. If you're young, claim you're a student and it's a school project. If you're older, claim you're writing an article about this service and want to know what they honestly think.
I was surprised that the seeds weren't all organic / heritage (or that if they were, that wasn't marked.) I could be wrong, but I'd expect the sort of person who goes through this trouble would likely prefer those varieties, and would be willing to pay accordingly. After all, somebody who is looking for the cheapest seeds isn't your dream customer anyway.
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All in all, I really like the idea. It's a bit like joining a CSA, except that it's located in your backyard, with the 'assortment of foods, for a fixed price.'