My warehouse/business was 50' from our house, and I dealt mainly with farmers, selling tools, hardware, and making hydraulic hoses. During harvest season, farmers work around the clock 24/7, which meant I did, too, since they all knew I lived next door.
Early one morning (3:00 AM), one of my regular customers got me up to make a hydraulic hose. The whole assembly was less than $10. As he was leaving after trying to get me to charge him extra (which I wouldn't do), he said that there was a $250,000.00 harvester sitting dead in the field, plus the 20 or so workers, truck drivers, etc., all stopped because of this tiny hose. I just thanked him, and went back to the house. He remained one of my best customers.
When my kids got into high school sports, I told my customers that I was going to attend their sporting events. If they needed something, they could leave a message on my answering machine and I would call them when I got home. They all respected that.
I did that for most of my good customers, and they kept me in business for 30+ years.