I wouldn't buy that sign even if I was a billionaire, because I don't see any significance in it. Yeah a dude held it and it generated some hype in Bitcoin community for a week - so what? In my book that wasn't a significant moment in Bitcoin's history. The fact that it was sold for $1M is just another example that there are Bitcoin whales who sit on large amounts of coins and can easily spend $$ millions on some overpriced stuff.
This is you sharing your own opinion on how you feel about it. On the other side, a lot of us wouldn't try to acquire any piece of paper or art that has no use to us, but these collectors, who like collectibles a lot, think differently, especially those rich Wahala's who are looking for means to spend and make some BTC and make things popular.
What I see here is that some people use money to get more money or fame. That paper is hyped and is the perfect piece to get the kind of attention they need. It could easily be sold out again to another wahala with just a little hype on it.
That's just it, most of this wealthy people does all this things to just show off or just to be among that few individual who have the financial power do it, it might sound stupid to the common man, but to the rich, it means a lot to them, and of a fact, this is just one of the stupid things the rich people spend more on, something they mostly don't need, and just as orpichukwu has already said, if they no longer needs it, they might decide to sell it to another crazy rich fellow, so that's just the reality.
And lastly, you also need to understand that most of this wealthy people sees money as nothing, because they have actually not faced what an average person usually face, so they spend money on things an average person will call stupid, just as this, so the truth of the matter is that, the rich, average and poor people all think differently.
For me I don't think it's only about the the show of, most persons just attach value to what they like. for what it's fought, people who don't have that much of wealth too would want to do same thing if the opportunity presents it's self, so at some point too the money to gives them the leverage to make people's passion come into fruition.
Sometimes people buy a painting of different inscription with millions of dollars which most people will see the painting as worthless stuff, However it doesn't show that they are wasting their money, they are buying things that are of value to them, the world may see it differently, but it doesn't change anything for the person that has bought it, because at the end of the day people will still have something to say regardless of the situation.