It’s rarely that clean. Sure, there is the immediate sticker price, but you have to factor in the migration costs as well. Depending on how deep the integration goes, it could take years of effort. All of which is going to take political capital to get people to migrate perfectly working systems without any operational gain. Plus you have the old guard who actively fight you-maybe they have spent their career in Oracle and that is all they know.

Even if you do move mountains and make it happen, suddenly any outages after the transition become your fault. “This never happened on the old system.”