When I was a student, I came up with the McDonald's Exchange rate. It compares the value of the same item in McDonald's in two countries. I use the beefburger or cheeseburger as a base. If it costs $1.99 in the US and 1 pound sterling UK, then you get a clearer idea of the value of the money. Since two bucks gets you a burger and one UK pound gets you the same burger, the value of 2 bucks is the same as 1 UK pound.
Snicker all you want, but that burger represent a lot of things, more than the bun and the slice of (what is supposed to be) beef. The price McDonald's put on that burger is a reflection of the cost of production of that burger meat including everything that makes up the supply chain before it, the cost of baking the bun, transportation of the items to the franchise outlet, the salaries of the staff, running the restaurant and every element that makes up everything that happens up to the point you bite into it. Now that price has to represent all that in 2 countries. So I think it is much more representative of the value of money than the exchange rate. You can't sell and buy the burger you bought to increase or decrease it's value.
I think this is much more saner than the system and the idea of valuation that people are using today, especially marketing types in tech companies that sell on-line in many currencies in many countries.