Starting this month with that last pricing update, we have moved to weekly pricing updates. So this is perfect timing for this thread.
Right now we have a damping factor on the prices, so even if the real world prices change dramatically in the course of 1 week, prices are capped at a certain percentage change, so they will more slowly adjust until they catch up to the real world prices. That way you don't have something where a game has a huge decrease in value just because there was a sale across the online stores that week. These values are adjustable, so once we are a few weeks in on the weekly update schedule we can take stock of how those price change caps are working and if they need to be adjusted.
Regarding games that are in high demand, we'll have to keep an eye on them, so far we've had good availability on most games a couple weeks after they are released. However, there is always the possibility we'll let the prices float a bit shortly after release for popular games.
While we want to stay true to our model of keeping close with real world prices, we will continue to tweak our pricing adjustment logic to help trades flow.
Also, one thing to note, once you are matched up for a trade, the price is locked in for your trade and will not change until you complete the trade. The "My Trades" screen always shows you the correct price for what you will get when you complete your trade.