Gabe NewellHere's my current thinking: Some people want to buy Half-Life 2 in a store. Right now we have three SKUs planned at three price points. One will have single-player only and not play MODs and we think of that as the mass market SKU (sold mainly at the Costcos and Walmarts of the world). The second is our traditional single-player plus multiplayer SKU that runs MODs and is sold at places like EBX. The third is the collector's edition SKU with lots of cool bonus stuff for people who like cool bonus stuff.
In the Steam world, some people will want to buy it once, like the middle SKU above. Other people will want to buy the game on subscription (e.g. $9.95/month). The good news for the "buy it once" crowd is, well, they only have to pay once. The bad news is that when we come out with new content (expansion products, TF 2, and presumably other games) then they have to pay separately for those. We're pretty sure that the $9.95 guys are going to get the better value, as we've been pretty good over the years at generating a lot of content.
Now nobody has done this before, so we're scratching our heads and massaging the plans to make sure we've got the best set of options. We've had some feedback that we should sell the top SKU (single-player only no MODs) on Steam, and my reaction has been "yeah, right, for the three people in the world who have a broadband connection, are sophisticated enough to purchase software over the Internet, but DON'T want to play MODs and multiplayer". Some people have said "I want a subscription, but I think the box and the manual are cool, so what about sending me those" and I think that's pretty interesting and we're trying to figure out what to do for them (needless to say Sierra isn't exactly jumping for joy at the idea of selling us boxes so people don't buy Half-Life 2 in stores).
But nowhere has there been a suggestion that people pay in the store and then pay a monthly fee on top of that a la the MMORPG.