Grifting on parts is a common business strategy. Sell your equipment at or slightly below cost, but make it up by the ton in part sales. Service agreements are even better.

But that isn’t the main issue. You should see how many people have sued John Deere over modified tractors that malfunctioned. And they tried to blame the manufacturer for the defect. These are very costly to litigate; even more so if they lose. Whether equipment was modified and/or whether the modification caused the injury or a manufacturing defect caused it is an issue of fact for a jury to find. You can’t easily punt those cases in summary judgment.