What is the total value of XRPs or the market cap of Ripple? On bitstamp today, $1 = 225XRP. That makes 100 billion XRPs worth $450 million.

Ripple's a payment system that can't be used to buy anything yet and it's transaction credits are worth half a billion.

Am I missing something here? Why is the price so high?

Edit: The price doubled since I asked this question. Now total ripples are worth almost a billion.

Edit2: Ripple people: you can down vote this questions all you want. It's a perfectly valid question.
Keep a few things in mind. Not all 80 billion XRP that OpenCoin is supposed to give away is already in people's hands. Also, the founders that kept 20 billion will probably not be likely to sell a big part of it. For this reason, the total amount of XRP in circulation is many times lower than 100 billion.

Beside that, it is true that the total market cap can be valued at 100 billion * 0.0044.. USD/XRP = ± 450 billion USD. But that number does not make too much sense because the price will drop very fast when people sell big numbers of XRP. The reason that the price has this (relatively high) value is because most people are not likely to sell their XRP and everyone wants to buy a little bit of them to experiment or to keep as an early investment.

The main reason why people buy XRP now is because they believe that Ripple has potential to become big some day. And possibly for development and testing purposes.