The sensor on my rear tire is broken thus disabling the distribution of nitrogen to that tire. I was told by a man working at the Mercedes dealership that a new sensor would cost $30 and labor would amount to $300. Does that sound accurate or am I being taken for a stupid young girl?? When I asked the man to provide his rough copy estimate to me, so that I could get it approved by my boyfriend, suddenly he couldn't find the rough paperwork he wrote it down on which made me feel that he wasn't giving me a fair quote. Please help me, thanks!