When Nokia's N95 came out onto the market, it was not immediately available everywhere but it was one of it's kind. And that was why it was able to command a premium. When the 8GB iPhone came out, was at $600 before Apple quickly lowered the price by $200 to increase demand.
This year, when the 3G iPhone was release, the price was $200-$300. Sprint's Instinct at $129. Still, there are smartphones coming out with prices closer to the $400 to $500 range.
Worth it? This is a tough one. A lot of phones out there in the $400-$500 price range are meant for entertainment purposes. However, I've not see one with the kind of internal storage the iPhone has. It's terrific a lot of these devices have a memory slot but if I'm going to have to pay $500 for a phone, I want to have a few GBs in there as well.
And in terms of productivity, netbooks are closer in this price range than ever before. The EEE PC can be found as low as $350. The sacrifice here is mobility but you'll have to way its sacrifice against increase productivity, a much bigger QWERTY keyboard, and screen. A friend and I often discussed this point.
On one hand, mobility is very important to me. Being able to take out my iPhone and start writing and get update information is very useful, not to mention very mobile. Taking a netbook, finding a WiFi AP or tethering it to a phone, takes an extra couple of steps but once set up, you're literally sitting on front of a true computer.
One argument for the netbook is the faster efficient chips that are being used. Intel's Atom chip is fast whether you're running Linux or XP. And if you're running XP, you are not missing anything in the Windows world as it seems like most of enterprise are holding onto XP as if their lives depend on it.
Having said that, there is something a smartphone has over a netbook right now. Battery life. With moderate use, the smartphone can last most of the day while a netbook's internal battery lists anyway between two to three hours.
Either way, you are getting a lot of computing power in today's mobile devices. You can't go wrong with a $500 mobile phone but you really should know what you're getting into and balance the needs between being mobile and productive.