Why yes, I do build wheels with carbon rims. There are two kinds of carbon rims out there. The high zoot type which are ~$800/rim or the open mold type for ~$300/rim. Carbon molds are super expensive so a company needs to be a big player to have their own molds (ex: Enve, Reynolds). A company that owns their own molds has more control over production, quality, carbon layup, etc. This all adds to the cost of their rims. Everyone else gets their carbon from just a couple factories in Asia. The carbon factory will have a number of “open” rim molds for anyone to choose from. Multiple bike brands could get rims from the same mold, each putting on their own graphics.
I’ve hand built carbon wheels with both and have no complaints. So, what’s your budget?