flippertyop I also know a couple who have used a surrogate in the States. In fact, they used two different ones. Like your friends' children, they will no doubt have access to the very best of everything, such as holidays, schooling and a secure, stable home, and the children have been much loved and wanted. I don't deny that.
But as PPs have said before, we are yet, as a society, to really fully understand the emotional and mental health implications that will come with a group of people being part of that society, knowing that their mother was deliberately excluded from their parenting; indeed, she was never intended to be in it. I cannot imagine how complex it must be to process that an egg from another woman was used to impregnate a totally different woman, and that money in the six figures was used to erase both of these women from your life from the minute you were born, so that you could be taken to a different country altogether. As a result, you do not legally have a "mother". The whole thing seems so distant, so transactional, that I don't know what could ever compensate for that.
14 and 12 is, sadly, prime age for the complexities of these feelings to begin to emerge, but without the emotional maturity to deal with them. I sincerely hope it does not happen to your friends' children, or the children of the couple I know, but the point is what if it does happen to most or even just some children?
Moreover, I dispute the idea that just because it happens in the US, it is ethical for the women concerned. There is a company advertising donor egg harvesting from Ivy League graduates (I can't articulate just how uneasy that makes me) and while surrogates can't be on financial aid, considering the low bar for welfare in the USA, I can't see that as being evidence that the woman is financially secure and not compelled to do this in some way.