Beware the numerator or denominator that shows up without its spouse.
A $900 tool that saves $2700 worth of manual labor saves you $1800 immediately AND makes you a viable service provider at $899.
A $900 tool used to repair a machine that generates $450 / hr pays for itself before lunch. The manual labor wouldn’t be paid back until mid-afternoon. These numbers get exponential if the broken machine is part of a sequence.
It’s easy to think of $900 as a lot of money. But in this case, it represents a numerator – it is a percentage of lost revenue and/or potential expenses (the denominator).