Steam allows you purchase a so called 'licence'-deal, if you are a computer café (or whatever the English term is), institution or something. Basically where you need a lot of accounts and a lot of licences. These deals are typically a lot cheaper than purchasing each individually.
That being said. I still think Paradox's games are more educational than Civ. In fact, I cannot really see the educational aspect of Civ4 right off the bat. Sure it has history build into it, but Paradox's games is playing history.
Nah. I think its selling point is the digital distribution. Purchasing the goods still require packaging and shipment. A lot of extra expenses. With digital distribution, the distribution cost is almost only going to keeping the servers alive. Which of course, individually is more expensive than packing one game. But considering how many games a server can distribute over time; it's a fraction of the packaging and shipment costs are on physical products.
Svip, did you not notice me talking about maths teachers? Civ4 is quite heavy on maths actually. I'm not talking about differential calculus and the like, but rather the basics of numeracy like arithmetic and ordering and decimal places etc. Once you've reached a level of education like you or I may have, it's easy to miss these things. Think about what a 10year old is likely learning though...
Regarding Paradox games, honestly I've never heard about them from educators. From what I understand, they are quite a lot more complex than civ4, making them much more difficult to use for education.
You'll find many people support the idea of using civ4 as an educational tool. For starters, it is much preferred over "shooters" and so forth which most parents and teachers still believe have an overall negative impact on youth.
Regarding schools purchasing a license to use Steam. At least where I live, that's highly unlikely. Even for educational purposes that license might be comparatively cheap, but it would be hard for any teacher to convince the executives to use up some of the precious budget on such a thing. Schools are already stretched enough with their limited funding. I suppose I shouldn't get into too long a rant, but really I just wanted to report that civ4 has been used on many occasions (or at least suggested) as an educational tool for children, and that I believe it is quite effective for that purpose.