People prefer to make their lives easier. There is nothing new or brilliant about this least effort principle, but it is quite useful in a negotiating context. People would rather say "yes" to a possible deal than complicate their lives by negotiating longer for a better deal. Buyers don't really want to look for new sources if they can find reasons to stay with old sources. Neither party to a negotiation wants to endure the stress of further negotiation or the work it takes to start over again with someone else. What's really important is the party that is willing to go beyond "least effort" gains significant negotiating power.