How we change what others think, feel, believe and do
List both the benefits of the purchase (the pros) and also the costs (the cons). Of course, the pros (the reasons to buy) will win.
You can even write it down like a balance sheet. Make sure the 'pros' column is longer and more impressive, of course.
Cons include things they wanted but are not getting.
Start with the cons and keep them short. But do make it sound credible, as if you are giving them fair consideration.
Then cover the pros. Perhaps sound pleasantly surprised as you describe them.
Sound reasonable, as if you are on their side.
Sound almost as if you are talking to yourself.
The Balance-sheet Close works by building Trust through appearing to taking a balanced and fair approach. It guides the other person's thinking and hopefully saves them the trouble of weighing up the pros and the cons.
This is also known as the Abraham Lincoln Close (Lincoln was a lawyer and often used this technique in his cases) or the Ben Franklin Close.