I think it is not logical that 1 stair costs more than 1 block, I mean : a stair is 3/4 of a block! I naturally thought it was a bug, because I know Minecraft Developers are logical and beautiful persons! The craft should be changed so that using 6 blocks you could get 6 stairs (and not only 4). Thanks for paying attention and sorry for my English!
That is not a bug, it is a suggestion. Please post suggestions on Reddit (http://reddit.com/r/MinecraftSuggestions).