I'd almost rather be locked in to a cheap, may-deprecate DB than a really expensive one. The former at least forces you to move, the latter just costs your business a lot especially when non-doers run the tech show and will sink money over re-impl every time (as opposed to making measured decisions).
FWIW, I found a table with prices for Oracle database licenses once, and it made Microsoft SQL Server look cheap. I am not sure if that means MSSQL is cheap, though. At least I am fairly confident that Microsoft is not going out of business anytime soon.
In my current job, I needed to get intimately familiar with the database our ERP software uses, because my boss needed lots of reports that the ERP software just did not do (unless paid an expensive consultant to customize the software for you). And the idea of having to move all that data to a different database makes me shiver in horror. I can understand why a business would be very reluctant to move their data from one database (both schema and engine) to another.
For business-critical tasks, I prefer a boring, reliable solution. But it is good to know that there are still interesting developments going on in the database area, building tomorrow's boring, reliable solutions.