These people didn't get on this milkfloat and then die because they were rich, they got on this milkfloat and died because they were cheap.
The posts upthread about other DSV's and the systems and cost involved show what the going rate of going down to 4,000m, and coming back alive, are - but these people didn't want to pay that, they decided that all that cost, testing and redundancy is for losers, and they would be fine going down there on the maritime equivalent of that forklift truck the A-Team turned into a tank that fires cabbages for a tenth of the price.
This thing isn't about wealth, it's about hubris - bad stuff doesn't happen to me because of Who I Am, and because I'm Always The Smartest Guy In The Room.
The kid is a victim of his overbearing father and the fathers pride, but the rest of them..