Take the train to AMS, spend a day there because its a neat place that can be seen without straying too far from the airport and the taxes are only $50 round trip so it should only cost you $25. Apply the cost saving to your train ticket and you basically get a bonus city to see and the loads are usually far better out of AMS. Just went a few weeks ago on United 65 open seats on the way there 45 open on the way back!