Arcen's prices are indeed so low (especially compared to, say, EA's $80-100 (what) titles) that even when I buy them at full price rather than on sale I almost feel guilty. Plus, the fact that I got Valley 1 and Tidalis free in a drawing plus a few expansions free from alpha testing (In these cases I feel especially guilty because I'm not good at giving feedback but I somehow have ended up in the alphas anyway.), I feel like I'm almost stealing from the company.
I buy extra copies for my friends sometimes to give more support.
There is a game called "Distant Worlds", a 4X space game that came out in 2010 on Matrix Games' site. Fantastic game btw. Base game is $30. Each of the 3 expansions is ~$25. Total price: $100. And no demos.
People moan and complain about the price, but my impression is the game is moving, because the designer is hard at work on the next expansion (a modding expansion).
Now I bought each piece as it came out, so each purchase wasn't a big deal (about $25 each time). I think each purchase was an exceptional bargain for the quality. And notice: no $5 price point on anything. $20 minimum. And again, my impression is that the game is selling pretty well.
Now $100 is quite a bit for the complete package. I don't have much comment on that. But except for sale periods, that is the game's price and the designer doesn't seem to mind.
I'm not familiar with this game, but I certainly don't think that the price is an issue. Starcraft runs you $100 for the main game and one expansion (with another one coming at probably $40 as well) so if DW is as good as you say then it's not a problem.
That said, I would never buy it. Not without a demo. I rarely buy games without knowing a lot about them. Starcraft is the most expensive game I own, but it comes with a demo and there are a vast number of tournament and personal match videos published that it was easy to tell that it would be a game I would enjoy. In most cases, though, I'll shy away from anything over $10 unless I have a chance to try it first. Almost everything I own has been bought on sale: Deus Ex: Human Revolution, Dishonored, Mass Effect (I actually got 1 and 3 as prizes for a contest and drawing, respectively.). So yeah, unless there's a demo I rarely pay full price for anything unless it's really cheap already.