The need to make money always makes things cost more.Most companies over here charge a fortune for very average parts. You'll pay $400 for $50 worth of carbon fiber. The cheapest 1.5" x 48" round tubes on eBay cost over $80. I can make the same tube myself for $15.
If it cost me $15 and an hour of my time to make that tube, I'd certainly be selling it for at least $80.
The real cost savings here comes at the expense of your time.
I'm building a large machine from wood, using a lot of very time intensive techniques. So, it's very inexpensive, but takes a lot of my time. I think carbon fiber construction is similar.