I may lower the price one day as an experiment eventually, perhaps after I release more games. I think that although it's too much for some people (particularly people people still in high school or college), many independent games have experimented with prices and found that 20-25$ is the only amount that really makes money -- if it sold for, say, 10$, it might sell slightly more (and it probably would not), but definately not twice as much, which would be required to offset the price.
There have been countless experiments that have shown this time after time. There have been hundreds of people who sold games for 10$ or 5$, raised the price to 20$ or 25$, and saw not only the total profit increase, but the number of sales increase. I mentioned some examples here: http://gmc.yoyogames.com/index.php?showtopic=302008&view=findpost&p=2130749
There's a psychological effect too -- if a game's only 10$ or 5$, many people think of it as a cheap game that isn't worth buying, or some kind of scam.
I'm very happy with the current rate (averaging 2 sales a day) which is a lot higher than most indie games, and especially good for someone's first shareware game, and everything I know about the history of shareware games tells me I it won't go to 4 sales a day if I lowered the price. In other words, it's not about what the game is "worth", it's about what it will sell for.
Also, see the last part of this interview for how the writer of the game's story justifies the price: http://kingludic.blogspot.com/2007/06/q-with-immortal-defense-writer.html
The game takes more than 3-4 hours to finish (although maybe you mean the demo section), though I really need to put in a timer to measure total game time (the way the Final Fantasy games do). I think 6-12 hours is more accurate though, particularly because the latter levels tend to be a bit longer and require multiple re-tries before they can be finished.
I agree that the additions will be good, but I don't expect them to increase sales that much or make the game any more (or any less) "worth" its price. I just want to do them because I want to perfect the game before moving on to the next.
E-commerce services don't provide hits or marketing -- that's not what they are for. They operate as the "shopping cart" type of thing. Using an e-commerce system is necessary because it provides a number of services -- accepting credit cards being the main one. And without an e-commerce service there'd be a delay for a person getting the game until I can get to my email and give it to them manually, which would be annoying to both me and the customers. E-commerce services also provide an affiliate network (which allows other people to sell my game and get a percentage), identity fraud detection, and so on. 9.5% is actually pretty low too, most of them go for 10-15%. Although one bad part is they don't actually send us the money for 2 months (!).
EDIT: I edited the title of this thread to mention the topic (whether the price is too much), since "Interesting" wasn't very descriptive.