They are actually fairly inexpensive for a type-R tyres.
..but yes More expensive than many road tyres for sure.
I'm not sure I would call them mild semi-slicks, they are as grippy as most type-R tyres and more grippy than a number I have tried, mainly because they are so soft.
For a modestly powered light car they are perfect for track use.
Not really a great day to day tyre since you will hear all the little bits of grit being sucked up by the tyres and thrown under your car.
They are a bit noisey as well, unsuprisingly, and also wear very quickly on the road as would be expected.
Certainly safe to drive from cold though.
Apparently they do have two compounds, medium and soft.
These should be translated to very soft, and very very very soft
Some countries can only get one though, I think it is "medium" in Ireland.