This sort of thing puts the wealth of the world's richest into perspective. In order to buy the island, Ellison will pay an estimated $500 to $700 million, which would be nearly 2% of his total wealth of $36 billion.
By contrast, the average value of wealth held by Americans is about $450k and half of Americans have a net worth of less than $100k. Depending on which of these measures you use for us normal people, the strain on Ellison's budget to buy the island of Lanai is equivalent to us paying $2,000 to $8,000 for property. For that amount, though, we would probably get an island considerably smaller than 141 square miles.