The final persuasion principle is referred to as "scarcity".
And, you most likely know this one already. It says that the more rare and uncommon a thing, the more people want it.
Many examples can be given here. Think of the "countdowns" on the home shopping network -- "There are only 678 more knife kits available at this fantastic price!" ... "Hurry, only 297 more TV's are available. Once these are gone, they are gone!"
TV pitchmen and others know they have to get you thinking that you must buy NOW ... or you will forever lose your opportunity for such an outstanding bargain. This type of persuasive pitch is used to sell cars, cookware, diamonds, doll babies -- and just about everything else in between.
The more you can create a feeling of "scarcity" -- the more people will want your product, goods or services.
It is well known that people often respond better to a pitch that tells them of a possible loss if they don't act now.
So, if you want to boost your response rate, be sure and emphasize information about wasted opportunities. You may want to say things like: "Don't miss out on this special offer ..." Or, "Only 10 more left in the store" ... Or, "Once this sale is over, it's over!"
You get the picture!