OP - I had the same experience at the comic book (graphic novel) shop. I was surprised how much I didn't fit in, even as a legit parent.
I can sympathize with all who had the 'you can't afford this!' line in their 20's. My wife and I walked out of a high end furniture store, but not before telling the manager we were ignored. The manager actually said to us, "I'm going to give you another chance to buy something in our store!" We walked out mystified. 15+ years later, they went out of business. Karma. Give US another chance? Sure.
BTW, we both had Mercedes in our mid-20's and again, treated rudely by many dealerships. It's definitely different as we age....too bad. Many young people have expendable income.