I just can't see paying 50% more for wire backing that isn't necessary for that performance. That's a huge premium. But each has his own priorities.My thoughts are that the RP's efficiency is nearly as good the Fram Ultra while still having wire backed full synthetic media. RP's cans are built to racing specs with 625 burst psi and overall it is a very heavy duty, quality product. I actually like the fact that it has an e-core because the wire backing will be absorbing most of the oil pressure so the e-core should never be too stressed while in all likelihood allowing for substantially better flow characteristics.
$14-$15 may seem high by comparison to a $9-$10 Ultra with wire backed media but the additional upgrades you get with an RP can should legitimately make up the difference to justify the higher price. I would buy an RP can filter without hesitation because I like how they are built.
Certainly the cartridge filter for the Pentastar has construction that is less different than the Fram. I seriously doubt there is a metal backing for that application. Not much room for that. (Which is why Fram used a nylon or polymer backing) I'd love to see one pulled apart.
I obviously don't have to worry about can thickness with a cartridge filter.