Drugstore Or Department Store

I have an obsession with MAC cosmetics I love them and who doesn't? My wallet that is who. MAC may be amazing but it is very expensive and I sometimes find myself wondering why? Why is this particular brand of make-up 3 times the cost of Revlon when they both make eyeshadow, lipstick etc. What is it about the chemical formula that is so different than drugstore products and makes it such better (supposed) quality. Is the only reason we are willing to pay $30 for eyeshadow is because of a brand? There is no difference except packaging, branding, and hype. But lets face it we will continue to buy MAC and scoff on Revlon because this is America.