But if you're a professional and depend on one being available at all times, it's part of the cost of doing business.
What if your machine was not faulty and repairable, but stolen, broken because you've dropped it, etc? There would be no warranty/repair at play there, and no replacement unit.
So, a professional should always account for a backup machine as a, well, backup as part of the cost of doing business.
If they can't afford a second machine, they can ask themselves if they can afford weeks without a machine and customers waiting for work to be completed, more...