The point is that the cost doesn’t matter. The government can choose to fund it if they want because social security is funded by a payroll tax that is separate from other discretionary spending, and could be maintained, increased, or decreased by changes to that payroll tax.

This is a good brief on social security: https://mattbruenig.com/2011/08/16/the-myth-of-social-security-insolvency/

There’s nothing structurally wrong with social security that would cause it to implode. It could be funded indefinitely by design, regardless of the amounts involved. That’s what I mean when I say that it’s a policy choice. The government may decide to make the choice to cut or eliminate it, but they will be deliberately choosing to do so, and they could just as deliberately choose to maintain it. The issue is political, not fiscal.