You are also paying insurance. When the project fails and blame gets assigned, you did the "right" thing.
If you hire an incompetent, it's your fault. If you hire Oracle and they send you an incompetent, it's theirs. Good luck with getting the money back though.
You're not just getting insurance... if the project is delayed or just needs a hand or two, Oracle will throw more people in to meet deadlines. If a consultant leaves the project, they will be replaced to keep continuity. But it all depends on how strategic an account you are to Oracle.
But yeah, nobody gets fired for hiring Oracle consultants.
It looks like you're assuming that the guys Oracle sends out to do the job are true domain experts, and that's a giant leap of faith.