Whenever I buy nearly anything negotiated (car, house, boat, large software license, other business deal), I simultaneously expect both parties to be reasonable and negotiate in good faith, yet all of those single-trial negotiations are entirely adversarial. It seems perfectly reasonable and fairly efficient to me.

I assume car sellers - especially for used cars - are negotiating in bad faith. It definitely seems to make the process less efficient. Standard advice is to get a car inspected by your own mechanic before purchasing. Dealers disclosing the results of an inspection and being trustworthy would be a more efficient process - it would avoid redundant inspections by multiple prospective buyers, and it would avoid people wasting their time on cars in condition that they didn't want to deal with, and it would avoid people who don't know how to play the game getting ripped off.

Think prisoners dilemma. A car /house/boat purchase is basically a one-off interaction - you’re not likely to be dealing with the same salesperson in 5-15 years when you buy your next car - so the strategy both parties should use is different from the strategy when it’s going to be frequent repeated interactions as in a workplace.

In the case of the car, it's definitely not a one-off purchase. People will go back to the dealer to get the vehicle serviced, and from what I understand this can (mainly for new cars) have a greater total lifetime value than the cost of the vehicle itself.

Even if this weren't the case, if you're ripped off by a used car salesman you will tell every single person you know that they're a snake.

Even if you don't do that, there are arbitration courts you can take them to to both waste their time and force a refund (VCAT where I am, I'm sure there's something similar overseas).

I really don't think it's in a used car salesman's best interests to lie and swindle.

You're mixing situations. I was imagining a NEW car sale, not used cars. In that case the product itself isn't in control of the salesperson, so there's no room for swindles there - but you have an adversarial relationship in terms of price, features / upsells, etc. That said, you're hardly going to blame the dealership if you get talked or dark-patterned into an upgrade you don't need or even regret. "Caveat emptor" and all that. We're so used to adversarial situations like that we blame ourselves more often than not.

A collaborative approach is a lot more like when you ask you're knowledgeable friend "what kind of bike should I buy?" and they ask you about your needs, goals, and budget then guide you towards specific options. They're helping you make a purchase, without pressuring you into something that's not useful to you.

>adversarial relationship in terms of price, features / upsells, etc.

I get what you mean now. As someone who "does sales" a fair amount in my work (owner of a second-hand video games business) the adversarial stuff is actually really frustrating.

I always try to give the customers the same advice I'd give a friend or family, even "downselling" them from a $100 purchase to a $25 repair if that would be more suitable, yet still so many people are adversarial and distrustful.

From my experience, this distrust hurts (non-expert) consumers even more than it hurts the businesses. Ideally, you'd have an honest salesman pointing out the pros and cons of all the different products so that the consumer can make an informed choice. Maybe that product that costs $50 will last for 20 years of continuous use, whereas the $30 version will break after 18 months.

Instead, because salesmen can't be trusted, they rely on their own instincts and buy products whose prices are completely uncorrelated with quality.

I've not done a lot of negotiated purchases other than cars, and car salesmen are notorious for negotiating out of bad faith.

The difference is that you buy or don't buy the car if negotiations fail.

At work you have or done have a job or even revenue if the only thing employer and employees are doing is trying to throw wrenches into the machinery to get the upper hand.

If you're buying a large software license today — and I bet this holds true for at least some houses, cars, other "high-pressure sales situations" too — the vendor definitely won't think of the negotiation as adversarial.

In an unending game of the prisoner's dilemma, either you all win or you all lose.

How is a house purchase not adversarial? For every extra $1K the buyer does or doesn’t pay, $950-ish goes to or comes out of the seller’s pocket.

I wouldn't use the term adversarial for this. Ideally in a house transaction, the main thing is that both parties want the deal to happen - the seller wants the money and the buyer wants the house. They very much have the same goal of getting the deal executed.

Now obviously all other things being equal, I'd rather pay less money (or charge more money)

But in most cases, neither the seller nor the buyer operating in good faith will really try to squeeze the other because losing a multi-hundred-thousand (or even million+) deal by being too anal about $1000 is in neither one's interest.

If a seller got very "adversarial" most buyers would say "fuck you, I'll keep looking."