Just limit the number of environments and keys that can be managed on each tier. 3 environments and 5 keys at the low end, 20 and 50 at the high end with a "call us" option for super heavy use.

Even if you can't rate limit in your current release it's in the license and when you can you move people up to a higher tier. This solves the issue of charging larger customers more without them getting more value.

Unlimited number of users, files, etc should never be part of a public pricing tier. Fine for a negotiated agreement with an enterprise that has a definite period - it's a great thing to concede to close an enterprise deal and should be essentially costless. When it is in a public price list it makes larger sales much, much harder.

I think this is a non-problem now. As of now, you want to grow your user base as much as possible. Since all your users are paying, you are not carrying a dead weight of freemium. Build up user count by any means possible. Only once you will see a significant drop in growth of revenue try to upsell current user base by adding important features.

Keep, for example, Cloudflare in mind. They have first built their user base, and once they were used by thousands of companies, they started offering additional options, Enterprise ($2K+) accounts etc. Focus on growth first, and keep some aces in your pocket for the time your revenue will stall. This way you will be able to be innovative whenever growth is slow, and there is a possibility a competitor will show up and take your business.

Thank you for this comment. I think it's spot on with keeping some aces in your pocket for appropriate time. It's not fun to keep onto unreleased features, but the product should continue to grow with time. If one wants to increase prices, ideally this goes along with added features.