Yes, it's expensive to you, but a Maglev would be even more expensive to everyone. You also need to park at or somehow get to the Maglev station, which may not be free.
By the time such a system could be built from scratch, you could instruct your car to go home and come pick you up after your return trip. The technology is already successful and perfectly safe now; ten or twenty years from now, technology will be even better and cheaper.
Changing existing laws requiring licensed drivers and working out liability issues could be quicker than building a Maglev system if not for the loss of kickbacks, union demands, and consulting contracts for friends that might encourage more public transportation.
Currently, you have several options cheaper than parking at the airport for a week: rent a car twice, or get sent by someone else (such as by shuttle services or taxis) twice.