“If you don’t take care of your customers, someone else will” is a business saying that has been popular since at least the 1980s. The origin of the saying is unknown. Management author Ken Blanchard has popularized the saying since the 1990s.
   
A similar saying is “The customer is always right.”
   
     
Wikipedia: Ken Blanchard
Kenneth Hartley Blanchard (born May 6, 1939) is an American author and management expert. His book The One Minute Manager (co-authored with Spencer Johnson) has sold over 13 million copies and has been translated into 37 languages. He has coauthored over 30 other best-selling books, including Raving Fans: A Revolutionary Approach To Customer Service (1993), Leadership and the One Minute Manager: Increasing Effectiveness Through Situational Leadership (1985) (in which he coined the term seagull manager), Gung Ho! Turn On the People in Any Organization (1997), Whale Done! The Power of Positive Relationships (2002) and Leading at a Higher Level: Blanchard on Leadership and Creating High Performing Organizations (2006).
 
Blanchard is the Chief Spiritual Officer of The Ken Blanchard Companies, an international management training and consulting firm that he and his wife, Marjorie Blanchard, cofounded in 1979 in San Diego, California.
   
The Ken Blanchard Companies
Legendary Service
If You Don’t Take Care of Your Customers, Someone Else Will
 
The Ken Blanchard Companies
Ken Blanchard Teaches that if You Don’t Take Care of Your Customers, Someone Else Will!
San Diego, CA (June 1, 2007)—Today, customers have unlimited options when purchasing products and services. And while most organizations recognize that creating customer loyalty is a key to creating profitability and longevity, it’s easier said than achieved. Help for those who struggle with customer service issues is now available from The Ken Blanchard Companies via its newly launched program titled Legendary Service.
 
15 December 1904, Woodbury (NJ) Daily Times, pg. 1, col. 4 ad: 
UNION GROCERY CO.
Our motto is, Take good care of your customers when you’ve got them, then you run no chance of losing them. We have both quality and price.
   
10 October 1965, Southern Illinoisan (Carbondale-Herrin, Murphysboro, IL), “Strike At Norge Plant Forces Move: Montgomery Ward Seeks Other Sources For Its Washing Machines pg. 3, col. 7:
“If we can’t supply our customers, someone else will. We can’t afford to give up business,” Christensen said.
 
21 November 1988, Augusta (GA) Chronicle, “Steve’s Tub and Tile Refinishing Offers Tub Refinishing At Affordable Prices,” pg. 8A, col. 2 ad:
“I saw a need for prompt, courteous service, where customers are treated right,” Steve says. “You have to remember that you’re in business to serve the customer, not the other way around. If you don’t take care of your customers, someone else will.”
     
Google News Archive
19 April 1993, Spokane (WA) Spokesman-Review,  “Small business wins extra points for being all-around performer” by Stefanie Craft, pg. A11, col. 2:
“Our business is strictly a service business,” Bob said. “I believe in that old saying, that if you don’t take care of your customers, someone else will.”
 
Google Books
Clinical Athletic Training
By Jeff G. Konin
Thorofare, NJ: SLACK, Inc.
1997
Pg. 112:
As the old saying goes, “If you don’t take care of the customers, someone else will.”
     
OCLC WorldCat record
If you don’t take care of your customers, someone else will : the importance of service quality
Author: Stacy Yean Wilbur
Publisher: 1998.
Edition/Format:  Book : Manuscript Archival Material : English
 
Google Books
Deliberate Success:
Realize your vision with purpose, passion, and performance
By Eric Allenbaugh
Franklin Lakes, NJ: Career Press
2002
Pg. 94:
“If you don’t take care of your customers, somebody else will.”
—Ken Blanchard
 
Luce and Associates
If You Don’t Take Care of Your Customers, Someone Else Will
Friday, October 1st, 2010 | Customer Service, Karen Peterson
Extraordinary service is critical for the success of any business.  Recently, I have been reminded how important this statement is!