Payload to orbit if all US main launchers launched simultaneously

[john smith 19]

What? That looks like the easiest problem to solve. Add another shift. Your rent and capital costs don't increase, just staffing, so your overall cost per launch is likely to go down, not up.

Wrong.

Human costs are the biggest on going cost. Where did you think the bulk of the $1Bn/yr NASA spent on STS went?
The estimated average full cost for a NASA employee or contractor is around $250k/ year. Pretty much any level of automation is a pretty good idea next to adding that to the bottom line costs.