Advertising tips: In your opinion, when advertising can become a huge money sink?

based on self experiance, if you have compititors with better prices, same or lower quality, then all your ads are useless, these days, customers are not always looking for the brand and/or quality in everything, you need to advertise wisly and not on every kind of media, advertising on social media worth it, and cheaper too, but as i said the prices of your service/product is the main factor