If memory serves me correct the servo cost me about $140 + tax/shipping depending on where you order it from. I can't find where I wrote the part number number down, but I should have it around here somewhere if I didn't throw the paper away by accident.
In my particular case it was the front passenger side air-mix control servo / damper, I could most easily manipulate the sound and actually watch it move its plastic arm when adjusting the pass side temp control setting to the extremes (max hot / max cold) with the controller in auto mode. The sound was present during normal use, but that's how I could make it worse in order to track the sound down when trying to determine which servo was making the noise. According to the dealer I talked to there are actually three servos for the A/C, two are located on the pass side and one somewhere else. Luckily only the one has made noise for me thus far, but from what I've read from the GS owners they have two that usually go bad... :(
http://us.lexusownersclub.com/forums/index...showtopic=53999
Plenty of threads from RX owners also:
http://us.lexusownersclub.com/forums/index...showtopic=21392