The way I look at it, $40 is pretty cheap. $40 for something that would likely give at least 20 hours of entertainment. Compare that to going to an amusement park, $20 for 3-5 hours of fun. Go bowling, that's around what, $20 for 2 hours these days? Relatively speaking, games are pretty inexpensive.
I've probably already gotten 40 hours worth of enjoyment out of my $40 purchase and I'm sure I'll be playing this great game for months if not years to come, especially if there's a strong online multiplayer scene.
$40 isn't much if the game proves to be one of your favorites but it would be rather steep for a disappointing game that leaves a bad taste in your mouth. I'd say that if you enjoyed the likes of Civilization or Alpha Centauri then you'll probably enjoy this. It's different, but you basically get to confront the same types of problems only with far less micromanagement. (Did anyone really enjoy clicking on squares to order your population to farm/mine it and then doing that over and over throughtout an entire game or micromanaging your engineers to build roads? It was fun the first couple times but became boring quickly.)
My best gaming buy was Unreal Tournament (1999) Game of the Year Edition for $10 back in early 2001. I've probably spent 3000+ hours playing that game, released a couple custom CTF maps, and still play the game semi-competitively online. (That's how awesome that game was--folks still play the Original greedily today.) I figure that I must have received hours of enjoyment for every penny spent. I hope Sins can come close to matching that.
