entrepreneur.com lists the top 5 traits of Sales Superstars. This one is Trait no. 5.
"Going above and beyond"
"The most successful sales-people go out of their way to lend a helping hand. As one customer told me, "We're not a company that looks solely for price. What's more important to us is the extra effort and degree of service we get from the rep and from the company. There's one sales rep who is outstanding in both effort and service. If we have an unexpected workload that exceeds our supply, she's willing to [do whatever it takes] to get us through the crunch period. We had a case where she even drove the product from Greensboro, [North Carolina], to Charlotte [for us]. Because of her, we would not change vendors for a difference in price.""
Jay, from Bangalore