I mean, only if the upper-class and lower-class are separate gene pools, which I don't think is the scenario you are describing, at least not over the course of multiple generations. Not with offspring sex being randomly determined, anyway. If a "lower-class" female is mating with an "upper-class" male, then in which direction does the genetic fitness gradient point for the children of such a couple?

Remember that (mitochondria and Y-chromosomes aside) it's not the case that sons inherit their genes from their fathers and daughters from their mothers. The children of an upper-class father and a lower-class mother will have half of their genes from each parent regardless of sex or class.

Thankfully, that's no longer the case! The miracle of modern medicine means that we can take the DNA of the billionaire man, and the DNA of the billionaire man's wife, combine them in an egg from a second woman, and implant it in a third. The third brings the baby to term, a baby that has none of her disgusting lower-class DNA.

Okay, but now this is mixing up levels of abstraction. The sex ratio is determined based on the fitness gradient of the genes, but this is almost totally independent of the incentives that drive the individual. Most people, let alone billionaires, are actually not consciously motivated to pursue technological strategies to maximize their genetic fitness, even though mutations that induce those drives might theoretically be selected-for. Perhaps that's why most men don't become sperm donors, and most women don't urge their sons to become sperm donors. Billionaires in particular tend to be more concerned about their legacy, estate, and inheritance, and having a large number of heirs divides the pile they've worked so hard to accumulate. But to each their own, I guess?

Biology is a great equalizer.

Being upper class and lower class apparently doesn't have significant biological indicator to affect strategies such as these.

The poorest among our society are still mostly drawing in the same amount of calories, and feel happiness and sadness, age mostly in the same way.

There are no indications that billionaires are significantly happier/healthier than us - in fact these indicators are mostly tangential with wealth past a certain point.

> The poorest among our society are still mostly drawing in the same amount of calories, and feel happiness and sadness, age mostly in the same way.

maybe post-Industrialization, but a whole lotta people died of famine and disease before then, and the ones getting hit hard were the poorest.