Charles, thanks for your feedback. With rising consumer wealth, better and more expensive goods replace inferior, cheaper Giffen goods. Designer sunglasses replace those from 7Eleven. The 200 Baht glasses in your example are at least equal (a perfect know-off) or better and less expensive than the original. This is a question of utility: you may derive higher utility/happiness/satisfaction from the 200 Baht glasses than from the original.

It's always possible to make something straightforward complicated with economics. Best, Manuel