Sometimes Money, Energy, and Time can be converted into one another.
Your 3 Personal Resources (money, energy, and time) can be converted between one another. You sell your time and energy for money, you use that money to save you time and energy.
Most conversions come at a cost, though. Time and energy are lost on commutes, which are often necessary parts of work (trading life energy for money). Also, buying products to save you time and energy can very much cost you time and energy in terms of acquisition efforts, maintenance, learning curves, and storage costs.