Anticipation, the build up of that excitement right before when you get what you ordered. Marketers use this element of anticipation and surprise in the most awesome way possible.
The factor of time is added in between the purchase and the product being handed to you. This removes the instant gratification factor. However, starting the moment you pay for the product you start feeling good about the purchase. This excitement goes on building until a tipping point when it starts to change to buyers remorse.
Marketers use this basic human behavior to time in the delivery of the product in certain cases, and the companies who are able to do this successfully end up making their customers feel much more happy.
This specific factor of anticipation now is carving out the whole business model of companies like Sprezza Box etc. Where you subscribe to a monthly box of fashion accessories for $28. The stuff you are sent usually is valued at over $100. Throughout the month, from the day you receive the box to the next month when you receive it, you are building up the anticipation levels within you waiting for the box to arrive.
This increases the good feeling of buying something. Try and notice it the next time some product gets to you a few days after you have paid for it. Also, for my Indian readers, cash on delivery might not work in this case..:P
Shivam Chhuneja