Then there reaches a point where extracting the data and moving it to some other system becomes such an implacable task that it is cheaper to just keep paying the renewal POs.

Is it really hard to extract data? That would appear to be an unnecessary friction and not in the interest of any serious vendor.

I imagine the lockin is all the custom code you wrote for the platform. The data is portable, even the schema can be reproduced in a fairly straightforward way. But all your bespoke automation code is not portable.

It shouldn't be, but there's always been very healthy industry niches around pulling data from one system and putting it into another one. Nothing ever lines up exactly, and there's always some idiosyncratic remapping or futzing that has to be done manually or with some one-off custom code, so it remains an expensive contract business.

The friction is in salesforce's favor.