I'm another one questioning how much reward there is for the effort. When I looked at the 'True Car' prices, it seems the difference between 'good deal' and a 'great deal' was a few hundred dollars. How much work to go from 'good' to 'great'?
I gather from reading posts about the subject of buying cars that for a lot of people, like Midpack, it isn't about getting the best deal for the least amount of time. It is about the sport of getting the best deal, period. It's a game to those folks, and the time spent on it is enjoyable, because after all, it's a game. They spend a lot of time on it because it is enjoyable, and the financial aspect is only part of it, and perhaps a minor one at that.
While buying cars isn't a game that is enjoyable to me, I can understand it. I've spent gobs of time building a radio control model, an activity that would bore most people to tears, but I've become so engrossed in a model that I'll suddenly realize that I'm tired, and then realize that "Gee, it's 2:00 AM and I have to be at work in five hours!"
At the other end of the scale, many people get all excited about a football game, which is an activity that bores me to tears. I've stared in astonishment at someone jumping to their feet and yelling at a TV screen and spilling their beer (a travesty!) over a football play. Just amazing, to me. Do they really think that yelling at a TV screen is going to affect the outcome of the play? Of course not, but it's a part of the enthusiasm for the sport, and that part is understandable.
So that's why so many people will spend weeks hunting down the best deal. It's about the sport, and the game of it.