For a 25000 mile award ticket, you're paying $425 (plus TSA fees) if your combined tax bracket is 20%, or $345 if your bracket is 40%. When the interest rate goes up to 2.5%, your cost is even higher.
rate | 2.02% | 2.50%
15% | $445 | $547
20% | $425 | $521
25% | $405 | $495
30% | $385 | $469
35% | $365 | $443
40% | $345 | $417