If you watch Academy sales, every few weeks or so, the Sigma goes on sale for $299 or so. I would bet buying a new barrel and paying a gunsmith to change it would cost at least that much. If it can even be swapped.
Nearly every day, I remind customers comparing the 9 to the 40 of the difference in cost of shooting.
It takes all of about 15 seconds to drop the barrel out of the sigma, But I am not sure that there may not be some differences internally between the two rounds regarding the feed function of the gun. R