Poland is a relatively inexpensive country, especially for tourists coming from the West. Cities are certainly more expensive than rural areas, with Warsaw, Krakow, Gdansk and Wroclaw being the most expensive ones.
Sample prices of selected goods and services in Poland:

Goods and services	PLN
Petrol (95), 1 litre	5,70
Double room in a ***hotel	350
Taxi, 1 km	2,20
Bus ticket, single fare	4
Lunch in a popular restaurant	25
Three-dish dinner in a popular restaurant	50-70
Pizza in a popular fast food restaurant	25
Coffee in a bar	5-10
Beer in a pub, 0,5 litre	10
National museum ticket	20
Cinema ticket	20
Theatre ticket	50-120
Train ticket Warszawa – Krakow, Intercity 1st class	135
Mineral water, 1,5 litre	2,5
Milk, 1 litre	2,5-3