$1 saved, $1 earned

Given two investments - 1) spend $100 to insulate a house and save $50/year in energy costs versus 2) invest $100 in a stock that returns 20%/year.

The first investment is obviously better - but do investors always see this? It would be interesting to compare similar investment decisions to see if there is a bias towards investing or saving money; or if not a bias, to see how often the correct decision is made.

Other potential comparisons - investing in a gym membership or other health preventative measures, hybrid cars, amazon prime, etc.

Presumably the decision to buy/rent living space started with a question like this one.