hehe, came here to say something similar, i.e. it would be hard to quantify the amount of resources wasted on convincing people to buy things they don't need.
Define "things you don't need" ? That's a very subjective qualification. Even things which may only bring joy to the end consumer but very little objective value otherwise still have the effect of raising the spirits of said consumer a little (or a lot).
Like are Magic the gathering cards "something you need"? No. Do they bring endless joy to people who enjoy playing MTG, do they help build supportive communities, etc? Probably. Is that net good for the world? Probably.
This reminds me of the rant of a friend of mine who works on movies and TV shows. Someone was telling him the entertainment industry was useless and doesn't bring value to the world. He replied "cool so if we took away all your streaming platforms, all your music and all your books you'd be totally cool with that?" . Obviously the answer was no.
Example of making people buying things they don't need would include sth like: a person who cannot afford to buy an expensive phone every year, getting one because of peer pressure generated by millions of dollars spent on advertising. I'm not talking about someone who would buy the same phone for their own pleasure, I'm talking about someone who would become socially excluded or mocked by his friends at school.
I'm talking about a generated need and compulsion over pleasure.
Things you wouldn't seek out unless you were first shown an ad.
MTG is a great example of the opposite. You seek out something fun to do with your friends. You happen to see an ad for MTG as fulfilling that need. Fantastic! Advertising works as it should.
But if I buy a print-on-demand mug as a gag for my sister's birthday, do I really need to spend the rest of my life looking at ads for novelty mugs? The gag is done. Nobody needs more mugs.