[wildgift]

I think the relationship is desirable, which is why some people will pay a higher price to have a relationship with a vendor, with the understanding that if s transaction goes wrong, the vendor won't balk at fixing the problem. There might also be an expectation that one party or other will extend credit for a few days.

In contrast, there are touch-and-go relationships all the time, like at convenience stores. You can't have the exchange without being present for the entire transaction, because neither party trusts the other.