Can this really be described as a "thread hijack" when the original topic has run its course and technically already gone off on a long tangent regarding the Ruger LCP?
Regardless, I think that you're underestimating the core appeal of firearms which mainly exist for the purpose of being unique, different, and just plain fun to shoot. The fact that the FN FiveseveN has remained on the market for as long as it has even at it's upscale price-point clearly illustrates that there are enough folks with interest in the 5.7x28 FN cartridge as well as pistols chambered in it. I think that Ruger noticed that and rightly figured that if they were to offer a 5.7x28 pistol at a lower price-point, they could attract the attention of those who were interested in the FiveseveN, but weren't willing to throw down over $1000 for a firearm that they only desired as a novelty range gun.
Granted that the Ruger-57 hasn't exactly taken off, but I think that has more to do with timing than anything else.
You may not understand it, but some folks don't buy firearms strictly for defensive purposes, some are just for fun at the range, and firearms with unique characteristics tend to have wide appeal for recreational shooting. Consider the Taurus Judge, the firearm folks love to hate because it's impractical, and inaccurate, and no true Scotsman would ever own one, and yadda yadda yadda. Meanwhile, it has been on the market for over a decade. Now granted, the popular explanation for its mainstream success is the arrogant, elitist assertion that only stupid, unattractive, inexperienced, [insert derogatory adjectives here] are buying the gun. In reality, many consider it to be an interesting firearm to shoot at the range. Yeah, yeah, I know... "There's absolutely nothing cool or fun about shooting a shotgun shell out of a Revolver!" Sure, there isn't. I mean, what could possibly be entertaining about that, right? Strangely, entertainment tends to be highly subjective, not everyone agrees, and sometimes what other folks find entertaining might seem stupid or boring to others. So much like how people buy the Judge because they think it's cool and fun, folks feel the same about the FiveseveN, the Desert Eagle, Coonan 1911s, AMT Automags, etc.
As for the concept of a Ruger-762 selling poorly because it would have to compete with old surplus Tokarev Pistols. Again, a widespread sentiment I have seen among owners of Tokerev pistols is the desire for a modern firearm chambered in 7.62x25 Tokarev. Furthermore, to use the Judge as an example yet again, Smith & Wesson makes their own version of the Judge known as the Governor. It's basically the same gun, only with a 6-shot cylinder and it costs roughly twice the amount of the Judge, yet it too has remained profitable enough for production to continue. So yeah, saying that a Ruger-762 couldn't possibly sell because there are cheap old Tokarev Pistols on the market is like saying that the S&W Governor could never possibly sell because the Judge is on the market, only worse because the Tokarev is a design which dates back to nearly a century ago.
The moral of the story is, don't assume that your own sentiments on any given subject reflect those of people in general, regardless of how correct you believe them to be. Once more, entertainment is highly subjective. Personally, I'm not a fan of Football and would never pay for tickets, especially not for front row seats, but others do, and that's okay, I'm not going to question it as though entertainment is objective and therefore such tastes are objectively wrong.