Question about some Steam games

Regional pricing maybe? As far as I know, if the developer or publisher (don't know which one :\ ) doesn't set a price in a region for a game, it won't be available for purchase.

This game is available to buy, so probably your region got its own currency recently and some studios didn't set prices for their games

Might be your location as I could see a buy button. I'm in the USA

Some developers haven't updated their pricing after the latest currencies have been added. You can check on steamDB - game you linked, for example

Sadly this is a pretty common issue for the countries included in the last batch of added currencies, all we can do is hope for the devs to fix it soon (or ask them politely/annoy the crap out of them).