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.
Although rich people has a different mindset and they easily identify things that can generate money for them no matter how the poor and average people see it, many things acquired by rich people today that's later sold at a very high price is just because it rotates around them, this things are been owned by only them alone thats why it gets much attention and hype, a rich man chase money at all cost but a poor man always evaluate risk because they understand the negative effect if they eventually lose the money but a rich perosn already know how rich he or she is, so losing a pinch will not have any effect on them.
Rich fellows take more risk to make money but a poor or average people doesn't see risk as a good thing, realistically most time this mindset of not taking risk at all keeps individuals in a particular state because I believe that calculative risk do exist and if anyone wants to grow financially, risk must be involved.