It is going to depend on where you live and who you ask...
Keep it more affordable by doing all the fab work yourself, cut the metal, fishmouth it, mark everything where you want it... exactly!!! do it all, and than just let someone weld it together the pieces, far cheaper than someone else doing all of that work for you. Business people tend to like being paid for the time they put into a project.
It is a simple matter of economics, skilled labor that is only performing 1 task is cheaper than skilled labor that requires many different tasks, setup, welding, cutting, layout...
Make sense?
HTH good Luck!
Rich