Right now Admiral, it is $10US on Steam, but they should be having another sale sometime soon and taking it to $5... I don't think they do a Labor Day Sale, but there should be something coming up in a few weeks, if memory serves... In the meantime, you can get the whole game on like Amazon for $20 US. Follow the link from the
SubSim Store here, and SubSim will get a commission on the sale.