Generally the cost will depend on the variant and year. You can get more information on quick and cheap key replacments from dealers or automotive locksmiths here.

You won't get your money back, at least not in the short term and not without a huge fight. Start by documenting all the visits to the dealer, what the problems were, and what work was done to fix them. Once you've done that talk to the dealer, show them the history of the car and ask them to fix it. If they will not co-operate go higher to Chrysler head office and talk to the customer assistance people. If that fails contact the company's CEO, Pat Dougherty, directly. If you don't receive any satisfaction for doing all of that enlist the help of a solicitor to send Chrysler a letter setting out your problems.

I've just been driving the latest Chrysler 300C and it's much improved and definitely continuing beyond Commodore and Falcon. It's not as good as the VFII, which you should choose next, but would work for you once Holden becomes an import-only brand.