I bought a used car last year. As one would expect, CPO offerings of the same make/model/options were noticeably higher than non CPO versions. In order to be CPO, you are buying from the OEM dealer, that is buying a used Ford from a Ford dealership, a used Audi from the Audi dealer etc. Sometimes that brings a slightly higher price to start with.
I ended up with a great deal on my 1-owner car from CarMax and bought a "Ford" Factory Extended Warranty from an online Ford dealership for less than dealers were asking for the CPO with a factory warranty. Ignoring the ext warranty vs non warranty discussion, I have the same, or better coverage as a CPO vehicle.