However, did you authorize the work done at that price. Was he given an estimate that stated that price, if not, then you will be a reduction. If he did know the price then he is SOL...
This is correct. If the dealer's fault is only that he charges too much, no matter what he advertises (but see below), and the customer is informed in advance what the prices and the estimate actually are, then the customer may be stuck paying those high prices.
HOWEVER, if the dealer is engaged in F-R-A-U-D -- charging for work not done, charging more for parts and fluids than the Dodge/Mopar list price, "bumping" the cost estimate just-a-little across the board on each item so that all-of-a-sudden the total is considerably more than the estimate, although no single item is VERY FAR out of line, or charging for work (whether done or not done) as part of the "standard 30,000 mile service," when in fact the work is not listed as necessary by Dodge -- then the estimate signed by the customer is likely of no consequence. The excessive charges are not excused by the customer's signature; the dealer's method of business (according to the examples) is still fraud. And fraud is one of the things a credit card user can complain about to his credit card company. AND, depending on what is learned from the dealer's response to the credit card company, there are plenty of civil service workers whose job it is to regulate errant businesses.
Another avenue of approach to this problem is to contact Dodge higher-up-in-the-chain-of-command. Does Dodge have an "ombudsman" whose job it is to investigate customer's complaints? If not, who is the western regional supervisor in charge of Dodge service facilities on the west coast? Does Dodge have a recommended list of charges for various types of service? They certainly publish and distribute (to their dealers) a shop-rate manual which includes estimated time of completion for almost all repairs; that's how a dealer arrives at many estimates -- consult the manual and learn the number of hours the manufacturer expects the repair to take; multiply times the dealer's hourly shop rate; perform the repair (if approved by the customer); if the repair takes less time than the shop-rate manual calculated, either keep the difference or (in some cases) charge the customer for the actual time rather than the estimate.
What did the dealer advertise? Did he represent that he could perform specified routine maintenance at a certain price, then charge more for that service simply because the customer agreed to the estimate before the work was done? F-R-A-U-D.
Perhaps it's time that TDR had a person dedicated to addressing issues like these on behalf of members. That would make TDR and the TDR membership a POWER in the marketplace.