Find someone with access to Manheim Auto Auction. They can pull up the latest SoCal auction prices and show you. Know anyone who works at a dealership? They can do it.
You can expect that the asking price at the dealer will be 20 to 25% markup from auction price. You can typically negotiate the price downward, up to 5 to 10% from asking price, depending on the dealership. Hope this helps.
With pre-owned LR3s, you can't always be as selective as when buying new. If you find the right vehicle for you, I'd say 'go for it' and don't worry too much about a few $ one way or the other.