The jet-setting billionaires hobnobbing in Davos this week are paying a huge markup for their Big Macs.

Of course, the world's most influential aren't really eat Big Macs. But if they did, they would be paying $7.54, or 6.50 Swiss franc, for the flagship burger at McDonald's (MCD).

That's according to The Economist's Big Mac Index, a "lighthearted" way to measure the value of a currency.

The average price for a Big Mac in America was $4.79 in January. The very same burger costs 57% more in the Swiss currency, making the franc the most overvalued currency in the index.

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It wasn't always this way. Just last week, the Swiss franc soared against major currencies after the Swiss National Bank decided to stop capping its value against the euro, a policy that had been in place since 2011 euro crisis.

On the other end of the spectrum, Big Macs are a bargain in Russia.

On average, a Big Mac in Russia will set you back $1.36, or 89 rubles.

Russia's currency has plunged to record lows in recent months as falling oil prices combined with economic sanctions have pushed the nation to the brink of recession.

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Neighboring Ukraine is the only other place with a currency that's more undervalued -- where a Big Mac costs only $1.20.

The Economist acknowledges that "burgernomics" is not a precise gauge of "currency misalignment."

One criticism is that Big Macs are typically cheaper in poorer countries, where labor costs are lower.

The Economist says measuring the relationship between Big Mac prices and economic output per person "may be a better guide to the current fair value of a currency."

Under that measure, Brazil has the most overvalued currency. The real is 68% overvalued, according to the "adjusted" Big Mac index.

Taking into account Switzerland's economic output, the franc is actually only 27% overvalued.