With my case, and I think many others, it wasn't so much the IAC valve being filthy it was the "hole" that the IAC goes into. You may want to consider removing the whole TB, removing the three sensors (IAC, TPS and MAF) and get the TB complete clean.
The last time I priced an IAC it was $55 from Advance Auto.
I tried to clean mine without removing the TB and it was OK but much better after I it was removed and cleaned;
Pic shows IAC opening as clean as I could get it without removal. The inside was still filthy.