Prices are at the rest of EU levels and yet the average salary is nowhere near......
Perhaps you should start by comparing the cost of meat and vegetables in Poland as opposed to Germany.
First.....I don't live in Germany.
So people in Poland just eat.....they don't dress themselves, have haircuts, socialise, TV/Internet, Mobile phone or any of the other 1000's of lifestyle choices people make that all cost money.
Meat and Veg is just one element of day to day life and well you know it.
Fuel prices.....1.58 zl per ltr.
All well and good if the only thing you will do is pay for your accomodation and food.
I took my father in law, my wife and myself out to the restaurant the other week in Warsaw....great little place by the University....not particularly expensive. Starter, main meal, drinks and 2 deserts and coffee....350 Zl....Yes I know I can eat cheaper......I can buy a kebab for 8 zl instead of a subway sandwich and fill my arteries with god knows what. Incidentally, coffee's are at least 12 zl these days.
I ate like an average European in an average restaurant and paid an average european price.
Imagine taking 350 Zl from the average Polish persons salary.
Sure, Poland is in the EU.....but life in Poland is not the same standard as the rest of the EU....Not yet.