For what ever it's worth, I based my bargaining with the dealership when I bought on the TrueCar prices. I ended up getting a price on the lowest end of the prices TrueCar reported. My circumstance was probably a little unusual though in that I didn't need to buy, and wasn't sure I wanted too, but I somehow convinced myself that if I could get a "deal" that was at the bottom end of what TrueCar said people were buying for, then I'd buy. Talking to a number of dealers I quickly found out they didn't want to go that low, but eventually much later, one dealer hit my target price so I bought.
So FWIW, my one data point is that there were several dealers were willing to sell me a car for the TrueCar "target price", but not for my own target price which was the low end of what TrueCar had reported. In the end, I kinda felt lucky that I had 2 dealers who wanted my business and eventually one was willing to sell me a car for the price I wanted.
I guess we all have theories about purchasing cars, but at the moment mine is that if you can get employee pricing or TrueCar pricing with almost no effort and are happy with that, then its a good deal. If you want more, then if you aren't in a hurry to buy and are patient and willing to work at it, then I think you can possibly knock a few $thou off that number. Now whether that extra few $thousand saved is worth the amount of time you devoted to it, that's up to you?
