The contrast principle affects the way we see the difference between two things that are presented one after the other. If the second item is fairly different from the first we will tend to see it as more different than it actually is.
If we first lift a light object and then a heavy object we will estimate the second object to be heavier than if we had lifted without lifting the light one.
How to use this – retail – someone asks to buy two things – show the most expensive item first as then the second item will look cheaper in comparison even if it is expensive for what it is. E.g. sell first a £500 suit and then a £100 jumper does not seem so expensive to the buyer. You will always pay more for anything bought after the expensive item.
If you present the lower priced item first then the higher priced item then the higher priced item will seem more costly as a result.
You can make the price of something seem higher or lower depending on what you offer before.
Same works for selling cars – agree the price first and then individually suggest the extras. An extra £100 for a better radio is nothing compared to the £20k you agreed for the car
If you give bad news (even fake bad news at the start) and then the real bad news then the real bad news will not seem so bad in comparison.
Successful International Project Management 