Now let me cover a couple of questionable closing tactics, so that you can defend yourself when they're used on you.
The Deliberate Mistake Close
As with any con job, the Deliberate Mistake requires a victim who also lacks ethics. The buyer baits the hook when he or she prepares a proposal and deliberately leaves out one of the requirements or leaves the quality standards vague on one of the elements.
Perhaps the element left out is the cost of stamping serial numbers, something the salesperson knows the law requires for recall purposes. The vague quality standard might be the requirement for copper-tipped switches. In either case, a knowledgeable salesperson would spot the mistake. An ethical salesperson would ...