and to compare profiting from resell something you purchased for cheaper to jumping off a bridge with your friends. you must be an extreme socialist who thinks everyone should just get everything they want for free. b/c buying and reselling/ trading is what built the country we live in.
Adding value to those transactions is what built the country we live in. Most retailers who don't add value to the consumer but simply increase cost don't last long.
Generally this works well when goods are "infinite" - ie it's unlikely for 100% of consumer products to be purchased and result in a situation with such scarcity. You do occasionally see it with new product launches and people reselling them immediately on ebay/etc, though, but this is very rare for consumer goods. If retailer A sells a product for $100 more than retailer B and provides me with no additional value, as a consumer I have the option to not purchase from retailer A and instead choose B.
It's therefore difficult for a retailer to just tack on a middleman fee which doesn't provide me additional value. Especially given the prevalence of online shopping. If I pay more for something, I almost always am paying for something - convenience, the ability to physically hold the product, etc.
This model falls apart with "finite" products. The middleman almost always adds no additional value to the transaction and effectively acts like a parasite where consumers simply pay additional cost with no added benefit.