I know of several businesses in my town that don't advertise. 100% of their business is by referral, or repeat business based on their product quality and reputation.

I told one of the owners that I'd given him a recommendation on a local chat board, and he groaned "I have more business now than I can handle".

If you have a high quality product that people desperately need, you'll have to get a stick to keep them away. It only takes one referral to get the ball rolling.