I could see an ultra rich scuba diver buying a hyperbaric chamber for their yacht. Decompression sickness is deadly and this is the only treatment. Hyperbaric chambers aren't common, there might not be one in an entire country. We get warnings about their availability when traveling. If you're diving off your yacht in a remote location, this could save your life.
That said, there's a step set up. Maybe they're shore diving at home and decided to splurge on something crazy and unnecessary.