The best I can tell you is that there ain't no bargains in NorCal that I've ever found.
For the last components/powder purchase a diligent web search took me to an old fave, Graf&Sons. Prices overall delivered made them way better than anything local and better enough than anything web. Whether or not they have the ammo prices you are looking for I can't say but a few years ago they were the way best source for flyer loads that I found - and delivered to the door.
If you come across a better source I'd be crazy to hear of it
10 flats is volume? HA! Go to Walmart or Dicks. You might find 10 flats between the two of them. As for Dicks...with the recent change in their gun policy, there probably won't even be a gun department there in a few weeks.
I'm in Paso Robles and I haven't found any great sources for purchasing ammo in person. If you go to the state shoot they have an ammo trailer that has a good selection at very reasonable prices. I can't remember who runs it.
It seems like Walmart in California doesn't carry any real quantities of target ammo. If you do make it to the LA area, there is a place called Phillips Wholesale and they have a GREAT selection at good prices. Federal Papers for $88, AA's for $80. I bought 5 or 6 flats the last time I was down there.
Besides those options, ordering online is the way to go. Most places have coupons or sales that get you free shipping and of course no sales tax for out of state purchases. It is great to come home from work to see a bunch or flats of ammo stacked up on your porch.