It's reasonable if your income is location-independent or you have plenty of savings. If you plan to work in Poland it's more or less the same as in other European countries or US. What you have to pay for living in euros you'll pay in Poland the same amount but in zlotys. However, if you want to buy, for example a smartphone or a laptop you'll have to pay it's value in dollars/euros exchanged to zlotys, so about 4 times more.

Nonetheless I think Poland has some other advantages over Western Europe :) I myself consider It a great place to settle for retirement.