I have to say I'm personally pretty allergic to fees. Even Stripe's fees are above what I really feel comfortable with, but I'd probably pay those to deal with payments less. Anything above 1% and I'd probably be out, to be honest.

As an alternative to a fixed percent, I'd feel a lot better about a model where the fee gets progressively less with a larger amount of users. This may or may not be a personal thing.

FWIW: I think the user you are replying to is honest but an unusual case.

5% on payments might be OK until things starts to take off.

Source: I've helped launch a successful business with Shopify and Paypal 10 or so years ago. Maybe could have saved a lot in fees but that solution was so nuch easier than the rest that it was easily worth it.

Edit: the webshop and payment solution was later changed to something less expensive.

Not the OP, but just another data point.

While it's interesting that you're thinking outside the box on pricing models, I would personally never signup for a login service on a revenue sharing basis - I'd much prefer a monthly fee (the standard SaaS model). The percentage also seems way to high in comparison to the value-add - Stripe, who actually process the payment, are taking less than you.

Having said that, I don't think I (or most of HN) would be the target market for this kind of login service.

But I wonder if you can find some kind of niche. Something for individuals and micro businesses that have no tech chops and just want an easy way to sell stuff. For that though, you'd need to go further than login, perhaps turning it into a WordPress plugin (or for another platform), and doing something to provide sales through Stripe, so the user doesn't have to build that themselves.

I think an issue to monetize this is that if you build a web app, you are going to have a way to send emails, and a "users" table.

Implementing email login on top of that is probably as easy as integrating with an external service, without the risk and the concerns about leaking user emails.