Buyers want to buy when you do not sell them

Retailers all over the world always try to sell a little more to customer, than he (customer) was going to buy. Probably that is why I see so many articles about increasing of Average revenue per user. And fortunately, it happens rather often for retailers. But trying to sell more, your store can loose customers. Why and how is that possible?

It is possible because of the factors that are listed below.
http://www.webinse.com/blog/buyers-w...not-sell-them/