Dropped $115 on a used refrigerant scale and it paid for itself on my second call
I kept eyeballing charges for a long time and guessing, which worked until it did not. Picked up a used scale off a retiring tech for $115 and used it on a fridge recharge the same week, and I was off by 4 ounces from what I would have guessed. That 4 ounces was enough to make the thing short cycle and the customer call me back, so the scale saved me a return trip and a bad name. Curious what other cheap tools you all grabbed that turned out to be way more useful than the price tag.