Remember, the factory sets an MSRP: Manufacturer's Suggested Retail Price. It's up to each dealer to set what price they will sell the car for. Usually with brand new designs, there is an additional markup until the impulse buyers are done, say 3 to 6 months. There are those who must be driving around in the hot new car to talk about and they are willing to pay more than others. Once that's done, then it boils down to how much supply versus how much demand there is on the dealer's lot. Shortages mean higher prices, cars sitting unsold on lots means discounts. One key thing to watch is what happens with the Mazda MX5 over the next few months before there are any Fiat 124s around. Is there huge demand and shortages? That doesn't seem to be the case so far, especially with the automatic transmission models. A black one sat on my local dealer's lot for almost a month before selling. Since the USA take rate for manual transmission cars is <4%, that tells me that the mainstream buyer isn't very interested in a new Mazda MX5. However, the manual transmission cars are very scarce, which tells me that the enthusiast buyer likes the car and is buying it. Two different directions, and probably too soon to tell what's going to happen overall.
As for the Fiat 124, well we haven't even seen clear pics of that model, no one in the press has driven one and written about it, so it's just too early to tell what all the differences are from the Mazda MX5 and how that will affect sales. Plus we know nothing about the pricing. It will become clearer as we approach the Los Angeles show which is rumored to be the reveal date for the 124. I'm looking forward to knowing a lot more about this car!