Pricing has been a mystery - it's hard to guess what the right price is for your game. Be assured - there IS a right price for your game. It is the overall most profitable price (sale price * # sales)
Taking Cliffski's advice, recently we started doing some A-B testing on our game price. For a two month span, we lowered our price from $16.99 to $9.99 had no noticeable effect on conversion rates. If anything, conversions went down slightly. We'll keep testing - but our ideal price may be higher than our starting price.
Your audience's perception of your game's "worth" is relative. Price is only one factor. How much value do they see in your game? Value can be replayability - alternate modes or achievements or even just randomization of gameplay. Value can be intensity of entertainment - is it "really fun/addictive", "really visually appealing", "fun story/characters or even "really good audio". Another factor is innovation - people rarely call it that, but if something is original, and they don't know of other games that are like it(free ones or more demos), they will feel more compelled to buy it.
Also the audience's perception is based on what source they are coming from. They may have price or value expectations. Hardcore players on steam are very sensitive to price. Causal portal audiences are getting more sensitive. In the case of our game - most players are new to digital download purchases - they just found the game on a flash site and got addicted to it. My guess is that is why they don't seem sensitive to the price - the haven't purchased many games this way before. Don't feel like you have to discount your price over time like a retail outlet - if you keep getting new players - the game is new to them - always act like your game is new, and people will be happy to pay full price.
My comments on the current casual portal price drops - the discussion is whether lower prices are "good":
I think the price wars are more important when you are working with "career casual game buyers" - who consume hidden object games like soap operas. I think a large part of the game club members are like this. The ones with less money just go demo to demo, so the portals need to get the price down to capture this audience. I don't think the lower prices are attracting NEW players, it's just getting more "lurkers" and demo to demo players to buy. Genuinely NEW players and audiences find a game somehow and get addicted to it, and buy a direct download game for the first time. These buyers aren't picky about price. As long as it's not over $30 they'll probably pay it. Later they will try more games and become price conscious.