I dont see them selling all that well. If you bought one and materials and labor all said and done paying 200 you would have to sell it for more than that for profit. If I did all of that I would want 300 and there is no way I would be able to sell one for that. I would only do it as a one off per person deal not a full quantity set. I used to fiberglass one off CAI systems but starting my own small specialty shop per say profit was never enough to think about or want to take it further. In my case they were custom application based so it was alot of work with each one so I charged not crazy amount but a lil more then what you could buy with a DIY kit. I also did other items as well but even just a few jobs on the table in a two week time period was very consuming with daily things.
Plus you would be up against alot of tough competition. Alot of major aftermarket suppliers and talented hobbyists like GugerArt. I personally wouldnt buy one if you made it because they are to feminine and wouldlook gay in any of my autos since it would be the only weird colorful object sticking out like a sore thumb. Might make an appeal to women but even they would more then likely pick something else that has tinkerbell on it or is pink in some way.
Not trying to be offensive just my opinion on it.