Yes, of course, there is nothing impossible. You may be in a situation one day that you are terribly in need of the cash and you see yourself selling the bitcoins for an amount not exactly at the main price self. Now, it also depends on the number of bitcoins the person have. You may have just one bitcoin and suddenly you need the cash that moment, and that is the only way you can get it, so you have no choice than to sell it.
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From @john-snow