I'm guessing they don't expect that many customers would actually convert if they had a higher cap on the free tier. It's more like a trial than anything.
The actual pricing will likely be significantly lower. Initially we thought of introducing a pricing system that's more aligned with the value created (with a generous credit system, based on number of actions taken), because we found that Salesforce charges by seat but in large orgs most of the seat companies pay for are unused, so the incentives aren't aligned. I'm not sure we'll go this way because people also want a simple and predictable pricing they can understand.
Or put everything free and have your own dedicated service, with your infra and support. Look at Sentry. Everything is open source. They are making a lot of money. Not everybody wants to run Sentry on their own infra. Same with CRM.