I recently bought a ski touring pack. It's almost certainly the best pack money can buy. The guy who made it has a waiting list and seems to be happy with his life. He doesn't advertise at all. If you find him, you move in the circles that mean that you want a high quality ski touring pack, and word of mouth will eventually reach you. If you really care about this category of product you can find him. The pack is competitive in price with anything else on the market of similar features and quality. It's not really a "luxury" or "boutique" product.

This is an example of how businesses and customers can be perfectly happy without any advertising. It's not the only example, just the first that came to mind.