The Mini is owned by BMW, and I believe the parts are just as pricey as other BMWs. I agree the Fiat 500 is new to the market, but I would imagine, just like other European brands, like Saab and Volvo, the parts and repair would also have a significant mark-up.
An updated mechanic’s labor cost book would have such information in it. But, they are pricey and not generally available for free on the internet. You’d need a subscription to a book service at a minimum. http://www.alldata.com/ is such a service