Yep. In business the money you've sunk into an old car is referred to as a "sunk cost." Sunk costs are not to be considered when deciding to get a new piece of equiptment or to keep the existing one. What matters is what money you'll save/spend on each one. If one is going to be a lot more expensive than the other, then you go with the cheaper one. It's kind of hard to apply that to day-to-day life sometimes, though.