As someone has mentioned, you need a mold. However, how you plan to make the carbon parts will affect your mold design. Also, do you plan to have just one piece, or will you be joining them?
You can make carbon fiber tubes pretty easily. If you're hand-laying up woven fabric, at this point the mandrel can be a piece of properly prepared pipe if it's the dimensions you want. You may not get a great outer finish, but sometimes you can clear coat the outside to make it look nice if you're lucky. You can wind or braid carbon tow onto a pipe as well. For real thin layers you may not even need an autoclave, but that depends on a lot of things. Long story short, for just the "mandrel" it's pretty cheap this way. You'd have to assemble those parts though.
If for some reason you're looking to make one big piece, you can use foams that are CNC machined to match a CAD file of, say, half the frame. The cost of this is up to the shop you use, but even just raw materials like high density tooling foams can get expensive. I'll leave it to you to look them up. After the labor to machine it, and if you're having them produce the frame itself too, all said and done I'd guess you'll easily be in the thousands of dollars when you're done for one frame.