Yah, I think claustophobia and fear of being crushed to death by great pressures/drowned might ruin the bathysphere idea for me too, but submarineing is something id like to do, remotely.
Though probly for a lot less, you can experience weightlessness on earth, feareffect, but then, its the awe of seeing the earth from space that would make 20 million worth it
imo.
I think seeing the earth closer up would be just as much a thrill for me. Every last corner! Imagine how many folk grow old and die never having seen beyond their own town/city/country, kind of sad.
I want to be dropped ontop MT everest by helicopter, screw climbing it! LOL