Hi Doggydog
I have lived in Warsaw and I have been many times in Gdansk. Warsaw can bee expensive but it can also bee cheap, it depends on what standard you prefer?,
http://www.e-mieszkania.org.pl/ is a site with apartments for rent (choose mieszkania do wynajecia) it's in polish, it will give you some idea on the prices. Food prices are 10-20zl for a polish lunch,4-8zl for a beer,BigMac&Co 13zl.
Warsaw is nice but personally I prefer Gdansk because of the water and the beaches!
Best regards