Why are future expenses considered less costly than expenses in the present?
Let's simplify this with an example. If I gave you $100 right now, at the very worst, you could collect interest rate on it (let's assume 5%).

Let's compare two cases:

A) I gave you $100 a year ago.

B) I give you $100 now.

In the first case, you'd have collected interest and now be at $105.

In the second case you'd only have $100.

Note this same logic applies to expenses. You can pay me $100 now.

Or you can pay me $100 next year (and keep the interest for yourself).