My friend has only 15k UA miles, and tried to go DCA from Austin this weekend. Ticket price is sky high, not surprisingly, roughly 6-700USD. I though she could get one way using miles (12.5k), but it gave another awesome option: roundtrip for only 10k+80USD (+additional fees, 40USD). It was a real bargain, and there was some award spaces available, fortunately. Never had such 10k=500USD value experience before.

It seems we cannot buy mile+money for "tomorrow" flight. I think it should be 2 days prior.