I don’t think it’s realistic to expect to get useful stuff for free. However you’re right that having all your data locked in with a provider that can arbitrarily raise prices is unappealing. Still, many people do find Notion valuable so they probably think it’s worth the risk. In the end it’s still possible to migrate elsewhere even if it’s annoying.

Your calculation is roughly correct but a p/e of 10 is kinda low so probably you can halve the numbers at least.