1) it's not just an investment in the asset.
It pays dividends. The asset can breed once per week, so that could be $1k+ per week generated.. paying for itself over time. Since this is the lone genesis kitty, its offspring could fetch a totally arbitrary value.
2) This is ethereum we are talking about. If the ether was bought 1 year ago today, it would have cost $1,557.1. Someone could have made a $1.5k investment 1 year ago which is now paying for itself weekly.