Before, when the 2 DDs were smaller children, we'd fly out from Canada. But from the time they turned 6 and 9, we have joined the masses who fly out from Seattle. From Seattle, we save anywhere from $500-$1000 when we fly to LAX, MCO, or Hawaii.
The overnight stay in Seattle (usually use Priceline to get a 3* SEATAC area hotel for $40), costs to park the car, or rental car (we like to rent the car to drive down, so we don't need to worry about leaving our own car in a park 'n fly lot), costs us peanuts compared to our savings.