California and its laws are an exception to almost any rule having to do with firearms. Don't take the word of anyone who lives in another state (including me) about how things work in CA; it's a full-time job just to keep up with their bureaucratic idiocy.
As I understand it currently, because all transactions (even private in-state sales) MUST go through a licensed dealer (FFL, or Federal Firearms Licensee) in CA, they have a state-enforced monopoly, and they take full advantage of it. You MIGHT be able to find a dealer that will do a transfer for less if you shop around, but I'm going to guess it won't be for significantly less money. Part of the CA transfer fee is dedicated to a background check, I believe, so that part is not able to be reduced by any dealer, and because they know you don't have a choice but to pay the fee, they have no real incentive to reduce it, as that would just directly cut into their profits.
Even in my rural state, transfer fees can vary wildly. In my town, the large sporting-goods stores charge $75 or more for a simple transfer (and here, there is no fee for a background check; all of it goes right into their pocket). Smaller FFLs in the surrounding rural county or nearby small towns, or the pawn shops right here IN town, charge $20-$25. Considering the small amount of actual work required to do a transfer, I can only conclude that transfer prices are deliberately set high to discourage transfers at the big stores. Many shops also state they will only accept inbound transfers from a FFL dealer or distributor; although federal law says they CAN accept transfers directly from out-of-state residents, many shops will not, because they have to be able to positively identify the seller in their transfer book, and it's difficult to do that long-distance (photocopies of Driver's Licenses can easily be faked or "borrowed", and this technique can be used to mask the seller and transfer of a stolen gun). FFL licenses can be verified electronically, but personal IDs like state DLs can't be linked to a face/body unless they are standing right in front of you, in most cases. If the store that ends up with the inbound gun puts a fake name in their books, or accepts a stolen gun for a transfer, they can be "dinged" by the BATFE during a routine inspection, or if the discrepancy turns-up during the investigation of the stolen gun. Too many "dings" and the store can lose its license, or the owner could get fined or go to jail. So to reduce their potential liability, they tell folks they will only accept inbound transfers from other FFL dealers.