Well, higher level rares will get better of course.

The point is, you could have spent maybe 15s on greens and another 15s on greens say at level 40, and you'd have a better armor. Yellow things are extremely overpriced because you can combine them for higher level stuff that eventually yields stuff that you can salvage for ectos, so the yellow price is not tied to their intrinsec value but to their salvage potential instead.