I sell a lot of cars on ebay and people used to do this all the time.
At the end of the day, when you set a reserve price you set it at the minimum you want for the car, so whats the big secret? You could save money by listing at 99p, which draws more people into bidding or start the auction at the minimum you will let it go for. Both would be cheaper than listing with a reserve. (Y)
Now I either ask for the amount I'd be happy with (Classified ad) or auction them at 99p.
You still get people who email asking 'How much to end the auction early?' or 'Whats the lowest price you will take for the car?' grr
If you have a price in mind you are better sticking to Pistonheads or Autotrader as they are cheaper than ebay and you get a better response. The only cars that sell 100% of the time on ebay are the auctioned ones. Fixed price or classified ones rarely sell well on ebay, I just stick them on to lure people to email me to ask what else I have for sale, LOL!