$40k * 300M = $1.2 * 10^13, or the whole GDP of the US
Okay maybe that's too luxurious for the common people. Let's say only 20k per year, and to only 200M people.
$20k * 200M = $4 * 10^12, or about the total federal spending for 2015.
So how exactly is the 'richest' nation in the world able to afford this, easily?
Also, this would presumably replace Social Security and other welfare costs (or retirees would be excluded).
And finally, people would still be working. I'm sure the taxes I pay would more than cover the cost for giving it to me.
I wonder if the argument against it is something like this: imagine for every person, they have some amount they are willing to contribute to said scheme. However, unless the total amount needed to fund such a project is small, if you don't force everyone to contribute then the cost will be significantly higher per person. Then, because it's higher than what some people want to pay, they choose not to pay although they would have otherwise. After that happens, the price increases more, and this effect continues.
But the question to ask is: does that justify the use of coercion to secure funding? I.e., does efficiency justify the use of force?