Isn't Glide pricing expensive?

I’m trying to develop a service site for users of my company’s products. The site handles your personal information and requires a password protected login feature.

If my understanding is correct, I should use the Private sign-in provided by the Private App.
The product has about 10,000 users, so I have to pay $ 20,000 a month. This seems too expensive. Is there anything wrong with my understanding?

Glide does not have a username/password login option. Available options are documented below:

Possibly. You only really need to use a Private App if you want to restrict who can login to your app.
For your use case - where you need to protect personal information - it might be that you just need a Public App with Row Owners applied.

I’d suggest that you review the information that Glide provides about data and user security, and then decide if Glide is the right fit.

If you really do need a private app for 10,000 users, then you might want to consider approaching Glide about Enterprise licensing.