I think Poland is just in the crappy position of not being on developers/publishers radars and being lumped in with other nearby countries when it comes to pricing.
I’ve heard similar complaints of polish people for all sorts of platforms, not only steam.
And I think them not having the euro probably adds to the situation since the value of the polish zloty has been going up compared to the euro.
So if publishers set the price to the euro equivalent in 2022, and the Zloty rose by 20% compared to the Euro in the mean time, you end up with the prices that are there now.