> free is not feasible, we start charging $20 per instance now

Same thing can be applied to low fees services. Look at bitwarden as a recent example, they doubled their prices overnight and hid the announcement in some useless blog post that no one reads, users found out later they are expected to pay doubles in any plan.. why? Because “that low price isn’t feasible we start charging $23 plus tax for premium now”

And the same things you will do to migrate to another when free -> paid you will do when paid_low -> paid_high if the pricing isn’t up to your expectations.

There’s no protection against this, it’s up to the business model change, investors, greed (aka scale up!), you name it, so regardless whether you are paying now or not, always have other options ready for when you need to abandon the ship.