Help determining if one-time-payment is viable?

I'm building a simple product, a QR code menu service, to practice my marketing skills and cold email outreach skills. Using the stack I'd like to use, it would cost me about $6/mo to run (just infrastructure) with PLENTY of room to scale for that price.

I'm building the product as simple as possible, basically just hosts a PDF menu and links to it via a QR code, with some analytics and such on top. I've also read a lot of people complaining about per month costs for these services. For that reason I'd like to offer one-time-payment per menu link/account.

However, I'm having trouble deciding if one-time-payment is viable. For example, if I charged $20 per account (which can host one menu), then I would need to sell one every ~3 months to roughly break even with my expenses. And that doesn't even include marketing costs or any other services that'd come up. Raising my price to say $99 would help, but I don't believe anyone would pay that for such a simple service.

Any advice about how other one-time-payment services make this work? Or ways to make this plan viable?