My son who is about 310 rides a nicer dept store bike however i did have to rebuild his wheel even though it came with a freehub. My son's bike is a 400 dollar bike from Wally World and came with a freehub but he kept on breaking spokes every 3 weeks of riding and that was with me doing a final retension on it. However after I rebuilt the wheel using DT Swiss double butted spokes, he hasn't broken a single spoke and the wheel has barely gone out of true after about 3-4 months of riding.
Its all about the wheels for big guys. For fun, I built up a cheaper Schwinn MTB frame from a bike that was new about 200 dollars from wally world. I put nice wheels on it, XTR derailleurs, Deore shifters, deore crankset, etc. It was as good as any lower end Specialized with all of the updated components even though it was a low end frame to begin with.