[naikrovek]

That's speculation. It could be worth just as much, less, or more if fully shredded.

Doesn't matter to Banksy. The gavel fell and the auction was completed before shredding began.

[geezerjay]

That's a highly unrealistic scenario. If any part of that highly romanticized story of how an anticapitalist artist destroyed his highly valued work in protest had any bearing with reality, by now you'd have the work's lawful owner pursuing civil and criminal charges for having destroyed his property.

Yet, all you see is the mainstream media spreading a story as a light-hearted oddity, as if no one was affected by this.

So, the only credible hypothesis is that in fact no one was affected by this, because everyone was in on the scheme and no one expected to ever be negatively impacted by this stunt.