Mine came to me with a Midas "football." Smallest converter I ever saw.
Aside from cost, flow, and size, installation is the other expense. I've taken the notion that doing your own exhaust work is like cutting your own hair. At least the results are less noticeable.
Having a shop bend, weld, and attach flanges by competent, experienced people in less time than you can go out and buy the parts is a plus. They can swedge the pipes to fit, and get you running in a matter of literally minutes. One mismatched pipe can leave you running around town to buy an adapter or rent the tool for hours.
Cost the entire job and all the parts accurately and you might be surprised letting a shop do the work is actually cheaper. I've had to clean up the sales counter more than once as a customer "estimated" the actual cost of doing it himself - and found it not worth his effort.