I had a son recently -- everything indeed went fine, but my wife and I did read up on both the risks and the permanent changes to women's bodies that having a child brings. Among other things, a C-section is not recommended an unlimited number of times, and it is classified as a surgical procedure for a reason.
You can pay somebody to get a biological child that you cannot have, but at the same time you are paying them to carry some risk for you within their bodies and possibly undergo surgery for you. I am not anti-surrogacy myself, but it just is not that simple as a win-win.