Hiya @dcki, and sorry to hear that things are confusing. I’ll try to bring some clarity!
At a high level, you can upgrade anytime, and we’ll automatically upgrade for you if needed to keep your site and services online. As a paying customer, our team is also very open to working with you on bills you feel are incorrect (“You billed me for adding my 6th user but I immediately deleted one, could you forgive that charge?”), so don’t feel like you’re “stuck” with a bad decision or an unused service. Also, since none of our subscriptions are more than month-to-month, downgrading by yourself through our UI is not a process that happens after your next 6 payments, but with the next bill.
To translate this into a plan for you: you could start on the free Starter plan while you develop, graduate to Pro once you start to go into production so you get 1:1 email support and a higher bandwidth and builds allocation. We’ll upgrade you to Identity level 1 when your 6th user becomes active (note that we count active logins within a billing cycle here - so if you have 100 invite-only users and 10 don’t log in within a month, that month will only show and charge for 90 users). Finally, you have time to make the decision before you onboard #100 as to whether you’d be better served upgrading to a different Identity plan, or instead a Business plan that includes that unlimited identity users. The “custom” pricing shown on the pricing page for Identity level 2 indicates that you’ll work with our Sales team to come up with a contractual price; I can almost guarantee that if you JUST want identity, the custom will not be cheaper than a Business plan since those contracts are generally much higher than $99/mo for you as a single developer managing everything about Netlify. If on the other hand you also have 20 collaborators on your Netlify team (this being people who use our administrative UI - not users who log in to your website using Identity) - at $99/ea/month - I’d recommend that you DO talk with Sales as they may be able to give you a price break at that volume.
If you’re interested in checking in with Sales, that is no commitment, and I’d be happy to have them reach out to you. That offer stands for as long as you are a customer, in case you want to start small and then talk to someone as your bill starts to grow :). I can tell you that our custom contracts can include things like different pricing for all of our features from bandwidth, to per-admin-user, to per-identity-user, and can include VIP tech support including a response time SLA and an uptime SLA, and a faster CDN as well. So, with that in mind, let me know if you are curious and want to hear from them.
If you don’t, no problem, happy to talk through things here and help you find the right plan