Customer service is everything when running a business. Let me rephrase that: good customer service is everything when running a business, whether it's a startup or a major corporation. Over time, consumers may not remember your company by what they bought from you, but they will certainly remember and associate you with how they were treated.
People tend to hold on to bad memories and bury the good ones. If a patron receives poor customer service, not only will they never do business with you again, they'll tell their friends by leaving a bad review on Yelp, Google or on your social media page, which can leave a permanent stain on what was once considered your company's pristine reputation.
Don't put yourself or your company at risk. Know what it will take to give your customers the best shopping experience and be aware of how customer service affects sales.