The opposite effect is that if you don't expect to deal with this person in the future again, negotiating harder starts making sense again. If you play soft to improve the relationship with some random trinket vendor in a touristy location for example, you win nothing. The difficult part is in correctly estimating which type of situation you are in.
If there are indeed zero consequences to harming the relationship, sure, you 'win'. In practically all real situations, there are consequences: You personally become inured to harming relationships, if it's a business transaction your coworkers get used to that as well. If your victim talks to other people you might do business with (either through networks you're unaware of - trinket vendor happens to have a beer with your hotel concierge, say - or just by leaving a negative comment on your business' social media, that has consequences. Or if previous people like you have played hardball with them in the past you might be starting out from a far worse perspective than if they thought people like you were generous and kind.
I personally can't stand it when rich foreigners try to get a souvenir for a few dollars less than the list price. That infinitesimal fraction of your wealth doesn't matter to you; but it could make a big difference to them. And similarly, I hate when I have to treat business deals as if I'm negotiating with a hostile enemy, when we can both benefit.
I didn't write "The difficult part is in correctly estimating which type of situation you are in." for nothing, and the hypothetical trinket vendor is just an example. Like you say, any situation where negotiating actually matters is unlikely to be about a one-time transaction.
That said, the GP comment was about trying to win the long game by sacrificing the short game, and I meant to point out that there is not always a long game and even if there is, not everyone subscribes to the same win/win philosophy and recognizing when your negotiating partner doesn't is a valuable life skill.
> if previous people like you have played hardball with them in the past you might be starting out from a far worse perspective
Yep, this is an excellent point. The interaction doesn't quite take place in isolation: it's in a societal environment, and your actions can return to you through that network in some form.
> If you play soft to improve the relationship with some random trinket vendor in a touristy location for example, you win nothing.
Is it really true that you would win nothing? I think that one might be a better person to leave just a little on the table rather than have that random trinket vendor right on the knife-edge between taking the deal and refusing it.
You'll find no shortage of people wanting to negotiate with you if you are consistently willing to give up negotiating leverage for feeling good afterwards. In the case of the trinket vendor, they won't spend a second thinking about that one tourist who negotiated better or worse than the other hundred tourists that day. There is nothing intrinsically wrong with charity, but I don't think you should delude yourself into thinking it's anything other than that. Personally I can think of other causes I find more deserving than trinket vendors in touristy areas but whatever floats your boat on that.
