It doesn't appear to be difficult to build a road car that does 200mph or even 250mph. When the Mclaren F1 came out, it felt like something absolutely heroic to hit 241mph...now that same sort of speed seems fairly routine.
I think it's not so much that it isn't difficult, as much as it's a problem that can be solved by just throwing stupid amounts of money at it. The F1 did the same in some ways I suppose, but the F1 had a clear design goal of being the ultimate road car. The massive speed and everything else is a consequence of that design goal and it was relatively difficult to achieve with some of the other limitations that the road car design imposed, like an NA engine.
The other icon of that era, the F40, is kind of the opposite in design philosophy I suppose. It was designed to be a great track car, no compromises to the driving experience for the sake of luxuries. I think because both cars have such clear visionary design they're quite impressive in what they've achieved.
Something like the Speedtail seems designed purely to inflate genital size. It doesn't seem like a car that's been designed to be great to drive, it seems like a car to show off with. There's almost nowhere in the world that you can get a car up to those speeds to start with, so it's largely pointless.
I feel like the affordable end of the market is shrinking while the crazy-expensive end is expanding rapidly. I guess I better get rich....
On the plus side, if you don't mind a bit of tinkering and maintenance, there's a whole bunch of really great sports cars from the 90's and 00's that are getting pretty cheap for what they are. Some are overpriced, like many of the Japanese tuner cars. But there's still plenty of great sports cars to buy if you're interested.
As an example, look at the prices of 996s if you want incredible value for money out of your sports car (add a couple grand to have the IMS changed out). They're unlikely ever to be a collector's 911, but that's exactly the point. They still drive great if that's what you're after, but you don't have to pay a premium for them.
And while something like the Speedtail is cool looking, if an average Joe goes to a track day I suspect they'd probably have a lot more fun in a prepped Miata than the Speedtail. Unless your life's wish is to go 250mph, I don't think you need to spend silly cash in order to get a great driving experience.