Ditto on what Tom has stated!
Carbons use to cost a whole lot more than they do now. Nowdays you can buy a dozen carbon shafts and fletch them yourself as cheap as aluminums.
As for the weight factor, out of a compound you should have no issues with penetration unless you don't have your spine correct. If that were the case, you would have your arrow coming out of the bow sideways, and that would be what caused your penetration problems, not the weight of the arrow.
If however you shoot say a 40 pound selfbow,
and you want to shoot carbons, you can always weight them up heavier to achieve the penetration you need. Gold Tips have internal weights, and there are also weight tubes for sale that will work on almost any brand of carbon.
In my experience, the only negative aspect I can find with carbons is that they last so long, I don't get to make new one's often enough.
My current batch of carbons I have been shooting for a year and a half with the same arrow wraps and fletchings. It's about time to strip them down and refletch them. The feathers are wearing out on me. :grin: