That's untrue. I know a farmer, who buys a John Deere combine before harvest. It stays unused until his harvests are done, and returns it by end of harvest season incurring $30k on this entire transaction. Why does he do that? Because he has two weeks to finish up harvesting or start incurring losses on his harvest. Farmer does care about saving costs/losses AND getting the job done in time.
That's interesting, why don't farmers run some sort of common reserve pools of vehicles, as a form of insurance?
Your entire anecdote is based on availability and not ROI/efficiency. Your farmer friend buys a combine (which is not a tractor - very different usage patterns and requirements) because he needs one for a very specific period during harvest.