Play · opportunity cost
Opportunity Cost Machine
Updated 2026-07-26 · Concept: every purchase has three price tags
A price tag shows dollars. It hides the other two prices: the hours of your life that earned those dollars, and the future value those dollars would have grown to if invested instead. This machine shows all three. It is not an argument against ever buying things; it is an argument for buying them with your eyes open.
Assumes 8%/yr growth compounded monthly, which is modest against the long-run U.S. stock average (~10%/yr nominal, per investor.gov). Subscriptions are modeled as the same amount invested monthly instead. A model, not advice.
For where your treasure is, there will your heart be also.Matthew 6:21
KJV. Jesus' point is not that spending is sin; it is that money always goes somewhere, and where it goes, the heart follows. Knowing a purchase's full price is how a steward decides what deserves the heart.