I used this index two days ago: my siblings and I want to buy a present as a group, but we are split across multiple countries and it wasn't clear how to make a fair split. We ended up agreeing that everyone would contribute their local equivalent of ~7.3 Big Macs.

The only minor correction needed was that the index lists the official dollar exchange price for some currencies while the real price is not even close to that, but that's not the index fault.