Actually, Nagoya to NRT, if purchased as one continuous trip, is slightly chepaer. I would be tempted NOT to buy the JR pass for this trip as buying point-point allows you to take Nozomi shinkansen and the pass does not.

If you are really into saving, you can buy your JR shinkansen tickets at discount coupon shops and save about 10%, but this is sort of "intermediate difficulty."

If all you want to do is visit Expo, a JTB "shinkansen" tour that includes the expo ticket may be cheaper, take a look at

http://www.jtb.co.jp/japannow/SUNRISE/sunrise31.html