Linux users were, on average, more generous with their purchase prices (maybe they offset the money they don't spend on operating systems?), and Swiss buyers were the most "generous," according to a metric that compares average purchase price to a country's per-capita GDP. The most generous individual? One "Stuart", who handed over $150 for a copy of World of Goo!
Meanwhile, the average purchase price for the WiiWare version was $15 -- because the sale didn't apply to that version.