^^ That i agree with.
Just go scouting for Counter-Strike alone.
Thats just ONE mod. Look athe weapons for that mod alone.
Then think about ALL of Half-Life 2! ;)
I don't think you can sell your mod for a small fee... I do beleive Valve would break your ass in two, since you are making profit from making a mod for their game and gaming engine... If you ask me they would not let something like that slide.