And again, I disagree with your assumption that these would be seen as elective. If gene modification could prolong people's lives by decades, make them less vulnerable to fatal injuries, or increase their resistance to cancer or other fatal diseases, it would be seen as a lifesaving technique. Medical science already does everything it can to maximize people's lifespans and keep them as healthy as possible as they age. Why would this be any different?
Because you can live a perfectly comfortable life without it. Most of the kind of things you are talking about are done once an issue comes up that specifically threatens a person's health or life. If there is no medical reason for this kind of stuff, it's not easily available to everyone. Even today, I believe most of the advanced prosthetic are either bought by the people with their own money, or provided for them by special groups. Insurance probably does cover it, but most of them will probably only get you the most basic versions.
Besides, the first people to get superpowers won't be the rich, they'll be the disabled. We're already at the point where prosthetics and corrective treatment are starting to improve on natural ability rather than just restoring it. Once people with disabilities and severe injuries are able to upgrade themselves to a superhuman level out of necessity, how long before healthy, "normal" people start thinking they need to upgrade themselves (whether bionically, genetically, or whatever) just to stay competitive? It won't be seen as elective any more than fixing kids' teeth is seen as elective today.
But once again, most of that stuff is still based around correcting a problem, and if there is no problem then you are probably not going to find insurance companies that are willing to pay for this kind of stuff. Insurance companies will do everything in their power, even let you die, to keep from paying for stuff.
And like Damian pointed out, even today some of the lowest level insurance doesn't even always cover that kind of stuff. I have the state insurance, and I don't have either. OK, I'll confess I think that was an option I just chose not to use, but the fact that it is even optional at all, still proves my point. I believe the insurances that you pay also charge extra for it, on top of all of the regular stuff. If it was really seen as the kind of absolute necessity you are talking about, it would always automatically be part of all insurances. Just look at how many poor people have bad teeth.
The problem with the "hoarded by the rich" idea is that it's applying capitalistic thinking the wrong way. Genetic enhancements aren't wealth in and of themselves; they're a commodity, and that means they would be marketed, not simply hoarded. There would be profit in making these technologies available to the public, in convincing the public that elective upgrades are actually essential if they want to stay competitive or be successful. The rich would profit more from encouraging the masses to get as many genetic enhancements as possible than they would from hoarding it all to themselves.
OK, hoarding it might have been to extreme, but it will be so insanely, massively expensive that only the richest people will be able to afford it, and I can't see any possible scenario where insurance companies would cover it. I'm not positive, but I believe that even countries that don't use for profit insurance will still make you pay for stuff that isn't medically necessary. So even if we get to that point some day, I still don't see this kind of thing being easily available to everyone.
After all, rich people don't want to be smarter; they already assume they're geniuses because they're rich, even when they're total morons whose wealth was handed them by their parents. They define their entire value by money, so they assume that if they have a great deal of money, that already makes them superhumanly smart and strong and desirable. And they can make more money from genetic upgrades by marketing them as a commodity, convincing the public that they need them desperately, as much as they need fast cars or fashionable shoes.
And they are going to want to make as much money as possible off of them, so they are going to make them as expensive as they possibly can.