R87 I'm not the original poster that brought up the ethics, but feel compelled to point out the irony of you asking why surrogacy has issues, but then followed up with: " Women have been being paid to have babies forever probably just like your mother." Childbirth was fatal until the 1920s when medicine caught up, but even now we don't have all the answers.
Right there it's the admission of what it is, paying for a human being. This is different than adoption because that child already existed. I take issue with IVF for any couple, gay or straight, and even when it's both parents DNA.
With the wealth gap growing, it's going to be a majority of women that aren't wealthy doing this "job". There's been plently of known exploitation that's come with this process-- more and more laws to break down the rights of birth mothers, while giving the outside party control over pregnancy. Plenty of cases of the outside party then going to areas of the globe that basically farm these women. Complex cases where there's difficulties, and so on.
I'm not trying to shame anyone that's done this, but trying to raise awareness. With outside parties wanting full control, it's also raised the stakes by including not just one woman, but two, because of the demand for no biological link (getting a different egg). Egg harvesting can be detrimental to womens health, without them being told this in a transparent manner. The medications are harsh, thus making women susceptible to side effects. There's an increased % of risks to babies produced from IVF, especially with an outside egg, that we're just starting to learn about. The surrogates are more at risk than usual because regular pregnancies are risky enough with dealing with foreign DNA in the body -- autoimmune diseases, poor reactions to pregnancy, and developmental problems.
Most surrogates working with agencies also have the requirement of having children prior, meaning the risks of pregnancy, like death, are on a woman that will leave her children motherless. The US has the worst maternal mortality rates in the Western world.
Until there's a way to produce babies outside of women's bodies, or we at least fix economic inequality with our healthcare, wages, etc., I can not find moral justification. This is just my personal opinion, everyone is free to disagree and do what they think is right. Again, it's about sharing all the information that rarely comes up with surrogacy and IVF.