Eiji,
I can't give you a number either, but agree that you should be able to get a much higher price.
If in your position, I would research the competition. For example, check out HNT Gordon at
http://www.hntgordon.com.au/index.html and see what he gets for his work. You might troll the SMC site for discussion regarding wooden planes and those who make them. I can't think of any other plane makers, certainly others have ideas.
I'd also look at the cost of the cabinet. What would you charge to make just that? And the mallet? I realize that the average price ($635 divided by 4 = $158.75) isn't a particularly valid measure, since there differences in the value of each item. If the mallet is worth $50, then the average of other items is $195.00, which seems way low. Subtract your cost for the irons (I'm guessing $40 each) and the average cost of the other items is $168.33.
I remember someone talking about selling clocks that he made. Of the many things he did that made sense, two stand out: 1) He selected a market place where people had money to spend, 2) After setting the highest price he could imagine paying for one of his clocks, he raised it by an additional 25%. He reasoned that what is a mortgage payment for you or me isn't much for someone with money (I can't use the term he did to finish the sentence, language police, you know) don't care that much about cost, and that most craftsmen don't really understand the value of what they create.
Jack the price by at least 25%, and if it doesn't work then give a discount. People like to think they are saving money and getting a good deal. If you double the price, you can give them an even better deal!
Good luck, beautiful work. I wish I had $635 to spend.
Richard