People are weird and irrational, and there’s much we don’t understand. Like why do shoppers moving in a counterclockwise direction spend on average $2.00 more at the supermarket?
Why does removing dollar signs from prices (24 instead of $24) increase sales?
What will work for you depends on your industry, product and customer. When you try to replicate what Valve did to increase their revenue 40x, it might not work for you, but then again, why not give it a try?
Here’s a list of pricing experiments and studies you can get ideas from and test on your own business.