Taking care of the customer is certainly one way to ensure repeat business, and customer referrals. But taking care of your employees is the way to ensure your business can continue to take care of your customers.
I've met too many business owners in my career that used employees as a necessary evil. People they must pay as little as possible to achieve the business owner's ultimate goals. And the real shame is that many employees of small business enjoy what they do to the extent that they put up with the ill-treatment given them by the owners.
With a very few exceptions all the investments I have ever made in people for my business have created returns many times over. There are always some bad apples that tend to make you a little shy of trusting employees too much, but overall my experience over 30 years has been over-the-top positive.
I found that if I respect and share with the people responsible for my business success, they will work hard to be sure my business is successful.
Take care of your employees and MOST of time, with your good supervision, they will take care of your customer and YOU!