Here’s a puzzler.

Although conventional wisdom has it that Apple (AAPL) iPhone users are more inclined to pay for apps than the owners of Google (GOOG) Android phones, a survey released Thursday by the market research firm Canalys found that Android apps cost, on average, more than two and a half times as much as iPhone apps.

In the U.S., for example, the cost of purchasing the top 100 paid-for apps in the Android Market is $374.37 — an average of $3.74 per app. The top 100 iPhone apps would cost $147.00, or $1.47 per app.

Canalys attributes the price discrepancy to two factors:

• Apple’s more mature, controlled retail environment, which allows in-app purchases and drives app price competitiveness
• With fewer people willing to pay for apps on the Android Market, developers have to charge that much more to break even

“Selling more apps at higher prices is the Holy Grail for developers,” says Canalys’ Rachel Lashford, “but achieving big volumes of paid apps on Android is no small challenge. More aggressive price competition around Android apps would help to encourage more consumers to make their first app purchases, drive greater download volumes, and ultimately be good for the vibrancy of the app ecosystem.”

Curiously, there is little overlap between Android Market’s best-seller list and the App Store’s. Only 19 apps appear on both top 100 lists. And when they do, they are often priced quite differently.

Electronic Arts’ (EA) Monopoly, for example, costs $4.99 on Android and $0.99 on the iPhone.