Firstly, I wouldn't spend $100 on a bar of gold if it was labeled "Thermaltake". Everything I have owned produced by thermaltake was junk, or quickly became junk.
$100 for any air cooler is past the point of reason when you could spend $40 on a cooler that will be within 2c and spend the balance on a better cpu or video card. The only reason to spend so much on an air cooler would be if it offered some other feature other than performance, i.e, it looked cool, was silent, or rolled and dispensed joints.
Another note, processor idle temp isn't really relative to performance. The total thermal load of a cooling system has very little to do with the idle temp, and idle temp doesn't affect performance of a cpu. Load temps are all that really matter, and the generally accepted max temps are quite conservative in my opinion. I wouldn't recommend burning a processor at 100% at 100c for days on end, but if your daily load generally doesn't utilize 100% of the cpu for long periods of time (like most people), than an 85-90c load temp isn't going to hurt anything.