And this exemplifies the point that I was trying to make. You don't need an FFL to ship to another FFL. No need to pay FFL fees on both ends...again, know the laws. The firearm(s) only need to be shipped TO an FFL in order for the transfer to be done legally. ANYONE can ship a firearm to an FFL.
You are partially correct, at least when it comes to USPS. You can (as an individual) mail a rifle or shotgun to a licensed individual. You cannot, however, mail a handgun. That requires you to be licensed. Why? Who knows, it makes no sense.
So, if you want to be able to use that sweet, sweet, low rate of USPS, rather than pay expided, rocket assisted, overnight express from UPS and FedEx, then you need a dealer to ship the handgun (which OP mentioned) to the local FFL. Now, if your Cali FFL wants to charge something stupid like $50 per gun, plus shipping, then it won't be cheaper. It all depends on which is the lower price.