I don't quite understand why people are still buying mining hardware. Currently it will take about a minimum of 4 months to pay off one card.
If I keep my $100 without spending it, how long until that $100 is free?
I fail to see your point. Explain.
I think he's trying to say that if you keep $100 dollars, it won't pay for itself. All you have is $100. If you buy mining equipment with $x, at some point, assuming it's profitable, you'll have mining equipment and $x.