I'm persoanlly not going to undercharge to get business, unless I'm not working at all due to their price's. When you undercut to get business you get the customers who just want something cheap, basically the pain in the *** customers. I'd rather have 20 good paying customers than 50 low-ballers, due to the fact the low-ballers are just going to complain to try to get an even better deal. Let them do all the hard work for low pay, when the word gets out you do the best job people will pay to have your service, rather than save a few bucks on the other guy. Would you rather do 10 cars for $200ea or 20 cars for $100ea? I'd rather make the extra money and do less work, but that's just me.
Also if you start out by undercutting, once you get popular and the appt book fills up your overflow will be going somewhere else.