Natural selection doesn't care about cost or advantage, only reproduction.

It is the sum of costs and advantages that lead to reproductive success. The trait is still here and still prevalent meaning people are still getting laid and starting families and presumably leading fulfilling lives.

I'm not sure what you are trying to say.

> I'm not sure what you are trying to say.

I'm saying, if it doesn't ruin lives to the point of preventing reproduction, then it stays in the gene pool.

Basically, I'm saying this:

> The trait is still here and still prevalent meaning people are still getting laid and starting families and presumably leading fulfilling lives.

As long as an organism isn't performing too badly, it stays in the gene pool. It can persist and even share its genes more broadly, if in diluted form, to the other more successful organisms. And then some of those mixed-genes organisms may occasionally express more strongly, but again not enough to affect reproductive success across the population.