If alpha planes is cheating then so is the blue screen in movies or matte backgrounds and they give awards for those. Sometimes it is not worth the time or RAM needed to create an object from the groundplane up. It is the end result that matters. I'm willing to bet you that had you not pointed out that the first image was an alpha plane, you'd have gotten many compliments on your modelling skills. Your lighting, and plane placement are fantastic and disguise the plane's flatness brilliantly.