What is Reddit's opinion of Earth Start Heavy Duty Reflective Mylar Roll 100 Feet Long - 2mil?

From 3.5 billion Reddit comments

So, this thing is 1.3e8 km^(2). Mylar off Amazon costs roughly $1M/km^(2)... so it at those prices it would cost 130 trillion dollars to make.

In practice, I would estimate that amazon prices are probably roughly 10x what you would have to pay if you were producing it in bulk yourself... so it would only take around 20% of the world's economic output to produce.

Of course, then there's the question of getting 5 billion tons into orbit (assuming 1mil mylar).

Incidentally, the economic math neglects material scarcity. Given that world plastic production is roughly 300M tons, it might take a little longer to do.