I have a different approach, if i have that kind of money 500 million dollar that's a lot of money, i will invest in a lot of things not just pure bitcoins because its hard to manage that huge amount of money and besides having in in one platform is going to be a huge mistake because what if the price drops? You should diverse it into different investments. If you focused on cryptocurrencies then invest in a lot of then bitcoin is just one of many. But i suggest that you should also invest in stock market because that's what the rich people do. If you want to be rich then think rich. Having a lot of money doesn't mean you're rich. Spend wisely.