Anything that brings Bitcoin to such price
Means it is dead and the system was flawed.
But wouldn't the price be zero in this case?
I think it's interesting to speculate about what type of event could bring Bitcoin down to $500 in the short-medium term (in the long term everything is possible). It must be a very serious event, but Bitcoin won't have failed completely, because this would mean the price is zero.
Some ideas and what I would do in this case:
1) Successful 51% attack, but attacker isn't able to control the chain completely but only for some blocks or, at most, hours.
Would I buy? That depends - if there was a specific flaw which led to the attack and it is fixable, then yes.
2) An altcoin surpasses Bitcoin and demostrates it is superior for several months. Bitcoin can't be modified to claim leadership again.
Would I buy? Perhaps, because at this price, maybe there's the opportunity for some wild volatility and I can make short term profit. Just like with altcoins, however, it's unlikely that I would hodl.
3) Extremely strong solar storm which shuts down the Internet and splits the Bitcoin mining network into several subnetworks (see
this thread).
Would I buy? Probably yes as the problems should be only temporary. But the question is: on which chain? If there are several subnetworks, I'd have to ensure the miners of my subnetwork have the highest hashrate. So perhaps it wouldn't be easy to profit from the moment of maximum panic, and once the network reconnects, it's likely the price again goes up at least to $10,000.