I just paid $53 for a battery contactor diode for a 1978 C182RG.  It is probably a $2 item at Radio Shack, but because it goes in a certified airplane, it was $53 from Cessna.  I had purchased the same part for a 1978 C172N about 3 years ago, and don't think I paid more than $10 for it.  Seems that Cessna is either trying to get rid of all of us owners who can't afford a new $400,000 airplane, or is trying to keep the company afloat with parts sales.  I was going to replace the plastic battery box tray, but they want about $600.  Thats more than a new battery.  Hopefully all the glue and duct tape will keep it going for a few years.  Thanks COO for letting me vent.