I found this research on the pay off of exceeding a customer promise very insightful. Please note particularly:
“The bottom line, Epley says, is that exceeding a promise may not be worth the effort you put in. “Invest efforts into keeping promises, not in exceeding them,” he says. And this advice also holds true for businesses, which should prioritize resources to make sure they do not break promises, rather than trying to go above and beyond.
To test this idea further, Epley and Gneezy asked participants in a follow-up study to imagine they had bought concert tickets for row 10 and then either received worse tickets than promised (row 11, 13, or 15), better tickets than promised (row 9, 7, or 5), or exactly what was promised. Participants were more negative about receiving worse tickets but were no more positive – nor more likely to recommend the company – when they received better tickets than promised.”