Please explain.

PPP is inherently tied to the basket of goods, but the baskets aren't standard. Even if they had the same products in it (they don't), products themselves can vary a lot. Some yogurt can be made from real milk made in a clean factory or can be a fake based on palm oil mixed in a dirty garage with rats and no health controls.

It also includes the cost of housing, so you end up comparing building-controlled and highly regulated areas like Bay Area with who knows what in India.