Just like smartphones are only for the super-rich? Technology becomes affordable to all over time.

I for one cheer on the billionaires trying to extend their lives - it will benefit us all, and remove much disease & suffering from this planet.

With smartphones, the super rich so not have the incentive to block everyone else from having them. Extreme pongevity is a whole different deal: those at the top do not want to be replaced, and what better way to do that by making it harder to get on their level?

Also, take inheritance. Business shark accumulates a fortune, then leaves it to his less competent children, who waste it, giving others a chance. Imagine a world where sharks do not naturally die from old age and keep their fortunes in best shape over centuries?

How you could stop the greed of someone wanting to sell those treatments to the mass market? I imagine Mark Cubin (or any other "shark" billionaire) would fucking love to be the first trillionaire or quadrillionaire by being the person who made accessible the treatments for aging. Cancer alone: the ego-boost and vast wealth for the person whose company/research helped "cure cancer" (hell, even just 1 type of cancer). these "sharks" would "chomp" at the opportunity I imagine.

If you are a member of an inner circle of an immortal oligarchy that already controls the most important markets, selling such treatments would effectively erode your already enormous advantage and fuel the would be competitors.

There is a lot of fake science out there and that could be used to reduce the market success.

Many (most?) of those original fortunes were amassed by giving large numbers of people small amounts of something they’d rather have than money. It’s not only that they’d keep their fortunes in shape (what you’re arguing is a negative), but that they’d have a longer period of time to create value (and capture some of it) in the world.

How is that going to work though? We're likely way past the carrying capacity of the whole planet-wide mesh of habitats, even if we make some huge technological leaps to reduce our adverse impact on the biosphere – right now, the combined H. sapiens biomass is about ten times that of all other non-livestock mammals combined, and just the space we take up is driving lots of other species to extinction. Cure aging and this will grow ad infinitum and likely outpace anything we can do to lessen this. I don't see people stop having children, most people are incredibly strongly wired to want them, and they're pretty important to how all our societies function.

So either you keep this cure away from most, creating an impossibly dystopian society of immortal lords and mortal slaves, or hope for a miracle like a terraformed mars within a few generations, or things are bound to crash horribly at some point probably not too far off.

That's highly speculative. Look at other tech revolutions and advancements: It hasn't always gone that way. The smartphones, cars, and PCs of billionaires aren't much better than that of normal people.

Did you ever notice that older people tend to be conservative and against the newer trends? Same people are often in power, having spent a life to get to their high position. If not for the fact that they have to inevitably die at some point, being replaced by younger people with less conservative views, they would be able to propagate their state of society indefinitely. Imagine if jim crow era politicians were still around, would they allow a black president to be elected?

Short life span is generally a boon for species as it improves adaptability. Taken to the extreme, bacterias evolve and adapt to everything precisely because new generations replace the old ones. Increase the lifespan of the humans in charge, and you get a total social stagnation, because all places at the top are occupied and you can't wait for the current occupants to free them by dying.

I don't know, the Kim family of North Korea has been staying in power for quite a while now. And wealth is even easier to pass down.