I guess the best value that I have actually used was spending 140K to get my family (4 of us) from DFW to LIH all on the same planes. The Perksaver Hawaii award was definitely a good use of money for us. Or possibly spending 15K for an upgrade to Business class for a flight to SIN. NW offered a "discounted" Y fare that where the 15K award was usable, but the fare was only about $1500.

A great value, but one no longer offered, was 15K for 7-days of unlimited inter-island Hawaii award. I really wish I could have that award again.