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.