Assuming that (a) we can sequence embryos reliably, (b) we identify a large number of genes that are considered favorable, and (c) we come up with a way of creating large numbers of embryos (eg: artificial ovaries) then the "quality" of the child in such a future will, generally, be dependent upon that amount the child's parent were willing to spend to find their best possible child.

Do you want a one in ten baby, a one in a thousand baby, or a one in a million?

The price will be proportional to the number of embryos sampled, on average. Since this is a competitive process, no matter how low the price per unit decreases the amount of spend, as a percentage of income/wealth will stay constant.