Here. Straight from the horse's mouth -
http://caag.state.ca.us/firearms/dlrfaqs.htm#18
18. What fees can I charge for handling a Private Party Transfer (PPT)?
If the transaction is a PPT, you are restricted to charging no more than $20.00 in State fees described and $10.00 per firearm for conducting the PPT. For example:
a. For a PPT involving one or more handguns, the total allowable fees are $30.00 for the first handgun, and $26 for each subsequent handgun.
b. For PPTs involving one or more long guns, the State fees are limited to $20.00 for the whole transaction plus $10.00 dealer fee per firearm transferred.
(PC section 12082)
and from the same Dealer FAQ page -
40. May I charge sales tax on the DROS fees?
No. On January 1, 1999, the state Board of Equalization ruled that the DROS fees are not subject to retail sales tax. Firearms dealers licensed pursuant to Penal Code section 12071 shall not charge sales tax on the DROS fees. Questions regarding firearms transfer fees can be directed to the DOJ through this website or by calling (916) 263-4887. Questions regarding sales tax can be made to the California Board of Equalization at its website
www.boe.ca.gov.
I might be mistaken, but it sure reads to me like a cap of $30 - anyone getting charged $80 is getting ROBBED.