At the <$500 level IMHO a bicycle... all of it, should be made of durable and relatively easy to replace steel and/or aluminum. I have trouble believing that the carbon fork and/or chainstays on a sub-$500 bike are any lighter than alloys, and they will be much more fragile! Competition riders take much better care of their bikes than any commuter or casual rider can, and it makes sense for them to have <13lb all carbon equipment. One day carbon will be as ubiquitous (easy to replace) on all levels of bikes as aluminum is now, but that day is not today. The cheap carbon fork will break, hundreds already have, usually not while in use, meanwhile 40 year old steel bikes are being sold for <$50 on Craigslist and they are (the frames/forks) as fit as they were when new. FWIW.