Part of the cost differential may be Conti's decision consolidate the S line and have only one flagship model, as opposed to tubeless and non-tubeless versions. In general, though, tires built to hookless spec to need to have tighter tolerances and tend to be a bit more expensive.
As far as that cut, it looks to be about borderline, IME, for a permeant sealant-only fix. I've had a few of those, right about 4-5mm, and would either just leave it or use a plug on it. Most of the time, it's just fine. One of my cuts like that, though, did re-open after about 1k miles, when I hit a sharp bump just right. It did reseal, losing about the same 25psi. It then went a few hundred miles more before another just-right hard bump made it re-open and re-seal again. At that point, it was towards the end of life, in terms of tread wear, so I just binned it. So yeah, it's probably fine, but if you want to be proactive about potentially avoiding another roadside inconvenience of topping off, you can plug it.