I spent a good portion of my twentys modding half life, CS, DoD, long before source mind you. I am in my early 40's now. I will not pay for mods. I had thought of downloading all the tools and modding some skyrim myself and if I liked it enough put it up for download, but not now. I am not going to take my time to one learn the tools, two spend untold hours making textures, models, animations etc.. to have it stolen by someone who wants to charge 5 dollars for a single weapon, helmet whatever. Far too many games get ruined when you start addign the pay-to-play mentallity. Do not misunderstand me, I do know the amount of work it takes to make good mods, maps, models, animation, items etc.. been there done that. But these are made for the love of the game, the enjoyment of making a new dungeon, pathing out the AI, scripting a fight etc... Learning the art of the craft, for some in the hopes of building a portfolio to try to get a job with a gaming company. I worked on many full blown stand alone mods for half-life/DoD but never for money. But I cannot justify paying for mods. Release your own indie game and charge for it, fine I may buy that if it catchs my eye. I can play this old game without mods, or I can quit playing it all together, it won't hurt me one bit to find something else to do. It may also motivate others to learn to mod to make their own things and never buy or download any mods. There are 2nd and 3rd order effects Valve/Steam etc... have not thought of, nor do they care about. They are a business, they care about money. If they can get more money out of you for an old game that you got cheap on sale, all the better for them.
