By harvesting, I assume you mean things like agriculture? If you are, then the reason is simple, supply, and demand, and the expectations of such goods being cheap. It is the water-diamond paradox; why is water so cheap in a lot of places compared to diamonds when you can’t eat or drink diamonds, necessary for life. Life is unfair is an opinion.

Manufacturing and certain services earn more money because of the added value. Manufacturing is not just consumer goods for residential people, but in a way, similar to service professionals, are also important for efficient production of higher end things at scale. For a service professional who is essential for business operations, they are more knowledge based and take up important responsibilities. Rich economies tend to be more service oriented, as they are in an advanced economy that needs a lot of professional roles to make the economy work.

Economies that are not advanced, will have less professional services, and tend to focus on simpler modes of production. These economies are usually extractive, mining, forestry, and at best, agricultural.

Because you can only eat so much food but you can buy stuff limited only by your amount of money

Depends on if there are many alternative producers, and if there’s a cartel.

For example OPEC makes big bucks.