The internet gives even inexperienced people tons of information to negotiate a good deal. Always find it funny that people constantly think they're getting screwed when buying a car, but they're fine paying 300% markup on their phone, data plan, clothes, etc. Buying a new car is about as transparent of a deal as you'll find in any purchase these days. This isn't the 80's or 90's when you had to go by their word; the information is out there for anyone with an IQ over 80.
I guess it depends on what "getting screwed" means. In the terms of used cars, I classify getting screwed by paying extra and getting very little for it. If I pull up black book price on Manhiem, then go to most dealer sites, the asking price is a +$10,000 markup on a car they paid ~$25k for. Depending on how long it has been on the lot, you can talk them down 2 to 4k. If you are patient (~ 4-8 months of looking), you can find the same car from a private party for close to the same price the dealer pays at auction, lets say $26k.
So what does that extra 5 to 7k buy you from a dealer? A mechanical check? You can pay a mechanic, you have done research on, to do a full check for less than $500. So, it must be the warranty? The chance of having a major mechanical that will exceed 4 to 6k is fairly low, the warranties can be full of holes (like add a mod and it is void), and it is in the dealers best interest to fix it just enough to make it out of warranty. Off hand, I can't think of any other objection that would support buying from a dealer as a good deal, but if you are an educated buyer and negotiate well enough, you can go from getting screwed to getting a fair price.
Everyone can be sold. An educated buyer is a tougher sell, but a good salesman can get emotions involved without the untrained public even knowing that it is happening. Most modern, if not all, sales books heavily incorporate psychology in influencing buyers. The best sales people can maximize their commission while making friends with the customer. The customer will then give up referrals because they think the sales person is the greatest.
On the tangent not quite related to the thread: I am not fine with buying all that other shit at inflated costs either, I paid 50% new price for my phone, data plans dont have much options, as for cloths, if you want to be a GQ motha fucka, you gotta pay to play, otherwise shop at the farm store and buy plain ass shit that was made to last (what I wear around the house). With many things you buy, if you want to put in the effort, you can get good deals on it.