For those of us that don't get sucked into these easily, more than anything it is probably that we just don't engage the sales person in the first place. I never purchase anything being sold these ways, but I can't really say I have given the sales person enough of a chance to employ these methods on me.

I have an aversion to anyone who is pushing sales onto me like this. Even if they were trying to sell something I would be really interested in, the method would cause me to avoid it.