The general concept is that while a "normal" at-will you get at 1 would need to double the base damage to 21 to keep up. However, in the case of a power designed to only be taken at a level around 21+, it could be designed to be useful at that level without having to rely on the extra damage thing to bring powers up to snuff.
I sort of wonder on this. I understand it makes sense, but none of the psionic powers we've seen so far do the expected at-will damage that you see on 90% of other epic at wills. I was really hoping wizards would update the at-wills to be better between releasing the psion and now.
Augment Powers aren't automatic. Everyone else gets the damage boost at 21st, but you can't get your first epic level at will until . And even then, everyone else gets the full epic boost at 21, psionic classes need to wait until 27th to get their second. And humans loose out a bit here, since they're stuck with a level 1 that doesn't scale and can't be augmented.
Some of the epic psion powers (monk aside) do fit into this. It's a shame none of them have an effect that's in line with non-epic at wills and deal extra damage, just to make the point. Concussive Detonation should, I think, there's nothing special about the rest of it's unaugmented effect... but the rest of the psion ones have some advantages vs what you'd expect for non-epic.
The ardent build we've seen, however, seems to be pretty weak in this area.
Exhilarating Strike, ironically, is only up to par because the basic attack you
grant should have the epic damage boost. The effect on Dismissive Strike seems decent (best opponent repositioning at-will in the game?). Perception Shift is interesting but only really good against opponents who don't target AC, and only one attack instead of all attacks until your next turn just feels too weak. Revealing Strike don't really do anything I could see a non-epic power doing. Hopefully the offensive build will have some 2[W] powers to cherry pick...
The 'middle' power point powers are very corner case ... but when they are useful they can be arguably better than full cost versions.
Yeah, the mid-tier are in effect 'free'. No one else can choose to use their 1st level encounter twice in a fight for a reduced effect, these are entirely a net positive to the power level of augment powers.