Nobody is saying you can’t have different classes of service or product offerings. But if I’m buying a banana or you’re buying it, it’s the still a banana.
Airlines can't directly tell how much money a customer has, so they find indirect proxies.
Business travelers (reimbursed by their employer and thus not very price-sensitive) have identifiable patterns. They prefer particular flights on particular days of the week, tend to buy tickets close to date of travel, etc. Airlines exploit this to charge them higher prices.
I do, however, object to firms aggregating any individual's purchases across different interactions. That data should belong solely to the individual and it should be illegal to retain enough information to aggregate interactions across interactions with the same customer.