Honestly the "more profit than the swap would have made me" part is true for that job but it's not why the math works out. The real money is that you charged $95 and spent 40 minutes, so you can stack four of those in a day instead of one board swap that sits on your bench for a week waiting on a part. Also that $600 hot air station pays for itself way faster than people expect, one dead X1 or Latitude a week and you're even inside two months. For newer Dells, Dell's own support site is hit or miss but the schematics and boardviews usually float around on Badcaps and the laptop repair forums, just gotta dig. Watch the revision numbers though, a schematic for the 7420 won't match a 7420 board rev 3 and you'll chase a ghost.

Used to figure the jig is set so it stays set, that's the whole point of a jig. Then I had a run of 30 cabinet doors come back with gaps you could see daylight through because a setscrew worked loose a little at a time and I never noticed. Now I cut a test piece every ten parts, no matter how good the setup feels. Sounds slow until you add up the cost of a redo, and a rattle call from a customer costs way more than ten seconds at the saw. Feelers are cheap and they don't lie to you even when you're in a hurry.