See, the thing is that most people think research or gaining knowledge – whatever you want to call it - is something linear, while in reality it grows exponential.
Let me explain a bit. Imagine we would have started in the year 2000 with zero knowledge but possessed the research rate we had in this year. By the end of the year 2010 we would have already researched everything we have researched in all the millennia before.
Try to understand that for a moment, since it's really hard to gasp and understand exponential growth or exponential functions for humans in real life. Humans are more of a Newtonian physics linear type of being.
Gaining Immortality in this context is just one more step for a scientist to archive and in the long run just remembered as an important point for humanity, like the pyramid, the first flight or the first a-bomb. However, this guy is not telling the truth or wants to lie, because we already accessed this technology like 8 or 9 years ago. Want to live a 100a more and look like in your 20s? No big deal, just give me 400-500 M€ and it's done.
And that's the thing. There is no infrastructure for treatments like this and one would have to build one for their own. Also, you need highly trained stuff and experienced research scientist in large numbers. Because everything needed has to be created first. And, eventually, you have to kill most of them afterwards, because they aren't allowed to possess this knowledge - yet. This is making it very hard to realize because very few top scientists are willing to hide for 30 years in a research lab or get killed for their curiosity on science.
In aggregation there are things in a large scale like this, which wouldn't go unnoticed. Despite the few people who even know about this, even fewer would be allowed to have access to this treatment. But the cure was only performed three times for now. The first success was killed - by me - the second was a failure because the plans where rushed, nobody listened to me, and in the end the needed processes couldn't provide pure enough reactant needed for further processing. The third was a success.
And that's why you don't see Bill Gates running around in his 20s. He does not know and even if he knows, he is not allowed to gain this kind of immortality. He only has access to clones of himself. He is allowed to have multiple ones but only show his true, initial shell in public, which he controls with his enhancement implant in the head of his alpha shell. And yes, movement of what one would call mind, consciousness or soul is possible from one shell to another.
Some years soon, the public sees some members of the "Elite" become really really sick because of a strange unknown genetical disease and the media is going to make a real drama out of this for you. They will even report that these people are so desperate, they have to take a new, experimental, untested gene therapy which could be the only way out for them. The treatment will not work, but as a bad side effect, the poor soul now ages in reverse till his mid-20s when puberty stopped. But this unfortunately requires further and constant treatment with a non-existing, but very very expensive therapy, which only elites could effort. In reality the just got their clone and transferred to it.

Good luck with your upcoming diseases!
(and FYI I'm just L A R P I N G)