Don't use a VPN or anything to change your country of orgin. That can get you banned. 

This isn't anything new. Companies figure out what price point by region is going to make them the most money. If they felt they could charge a single penny and make the most money, they would. 

No i don't use VPN. I have used once when I was on holiday but I connected to my country server. There was propably some glitch in connection today. I wouldn't mind if avg ex rate was higher than market one (e.g. if avg USD/PLN is 3.91; then in PLarium shop it would be always +0.5)- this is normal market behaviour. But paying twice as much just because I have different local currency? A bit unfair in my opinion.

And of course if content of the packs would differ but As I am checking sometimes deals using calcualtor from hell hades, eaach one is marekd as trash one and now I know why.

Exchange rates aren't something Plarium controls - it's set by the different shops the game is distributed in, eg by Google or Apple.

If that's the case then why if my transaction currency on both phone and computer is the same, on the phone transaction goes through google play and on computer directly to plarium, but when on the phone my currency for some reason was changed to USD, the difference was considerable and still on computer I had same values in plarium shop? As I mentioned - if the case was difference of +0.5 to the avg market rate - no problem. but if in USD you can buy 2 items while in local currency only 1, then it seems unfair.

I'm not sure I understand your question. You seemed to have answered it yourself - on your phone you're using Google Play, and therefore currencies and exchange rates are dictated by that store. On your PC you're using Plarium Play, which means they arbitrate that stuff, probably through some third-party exchange service. In either case, Plarium is not the one doing the currency exchange, so they don't control what rates you're offered.

It could be that perhaps you opened the game using a browser online and it linked to some kind of IP back in the US compared to where you normally play. I know I saw that happen to me before as well and I got a different currency instead of USD and then it changed back.

I'm not sure your real issue though. If the prices are too expensive, then just simply don't spend money.

FWIW: Different platforms (iOS, Google Play, Plarium Play) have different pricing on top of ones location affecting prices.

You dont have the option of paying in Euros?