If that happens im going to buy a lot, but since its just a dream since , there is no way we are going to see that price, and as other said lots of people will buy, since they know what can happen a few bitcoin in that price is enough and keep it, sometimes you need to gamble on something, since we never know what could happen next, only people know the real value will not think twice.
Not saying that this can't happen but there are things that are practically impossible to achieve even small. Bitcoin in the last 5 years never for once mistakenly dump to $500, even when there is market arbitrage, you hardly see such. Bitcoin market with low liquidity hardly go this low, so this is not something that is going to even happen. If we ever see this kind of price slash with Bitcoin, that means that we are doom because it's either the world is against Bitcoin finally.
I don't want to be selfish but I will be happy if we are going to be having Bitcoin cheap again. Just imagine having a whole Bitcoin cheap as $10k, I'm not too greedy like OP who is asking for $500, I need just $10k figures Bitcoin in that amount and I will sell everything all I have to get it. I know I'm going to recover in the next 10 years or even lower and I don't even have any reason to sell, I will get money elsewhere and never think of going broke again.