Here's probably the worst example I picked up on:
Mind Thrust (lvl 1 at-will) vs. Psychic Brand (lvl 17 at-will).
I think the key to Pychic Brand is the huge damage boost given to the party for each hit. This power is like turning the target into a pinata. They can't hide, and every hit against them gets a fairly large boost to damage. Skillful party members will use this opportunity to use their multi-hit attacks to crank the damage even higher.
Also just because it costs half as much as the other augmented power, does not mean you can use it twice as often. It may turn out that the creature dies before you can use it again.