Silly but clear
First off, I do find this a bit silly; it really does seem fair if a virtualization product limits use to x cores, you should need to pay for x cores. I mean, if someone's stuck a copy onto AWS are they then liable for like a 8,000,000 core license or whatever?
That said, I thought it was common knowledge that Oracle has pretty strict licensing terms, and that they are pretty strictly enforced. They may just have to suck it up and migrate to PostgreSQL or something if they are wanting to be able to have their DB floating around in the clouds.
I suppose a practical solution to mitigate this would be to segregate off an Oracle-only section (enough for redundancy) so the Oracle stuff stays there, and everything else runs in the rest, so you'd have to fork up for that section but not the whole data center (at least in the future, I guess you may be toast and just have to negotiate that huge bill down for past usage.)