And see Tesla knows this, which is why the margin on their cars is higher than most.
You may have disliked that sales experience with a dealer or used car salesperson, but it quite likely got you a slightly better deal than had you tried to negotiate yourself.
This obviously won't last, but just something to consider.
My first Toyota dealer experience was offering to buy a car at advertised price, and them refusing/countering with a lease. We just walked out.
Based on that, I waited until Toyota offered pretty good unadvertised discounts and called up a bunch of dealers with an offer/car in mind. I got the car my wife and I wanted for $1k more than my offer, which was I think $9k less than MSRP, and the experience was way better. We only had to sit through the finance departments upsells.
The third sale was paying MSRP at a Lexus dealer and we still were there for almost 5 hours.
I think these numbers are better represented in percents rather than absolutes. $9k less than msrp on a Corolla seems unobtainium.
Buying a Ford was the worst experience I've had with a new car, but that could have been entirely on the dealership.