Ever go to get your oil changed, only to leave with a much larger bill than you planned for? 
Don’t feel bad, this isn’t always a bad thing, as some thorough mechanics can actually prevent untimely breakdowns by catching existing trouble-spots before they become breakdowns. It’d be awesome if every repair shop actually worked like this, but unfortunately, many shops will try to squeeze you for unnecessary repairs, simply because you lack the knowledge of vehicle mechanics, and they’ll try their best to take advantage of this.