Basically every place in Poland is cheaper than Warsaw. Comparing any Polish city to Warsaw economically will give the obvious same results on every aspect, but these cities are completely different breeds of horse. Krakow is more visually appealing and is loved for its historical and cultural value, and a kind of bohemian vibe. Business has boomed significantly during the last decade down there and it's getting more attractive. I've heard it faces serious pollution problems, and in some areas crime is more significant than in Warsaw (which in general is a pretty safe place). When it comes to 'big city life', making money and riding on the fast lane in the land of opportunities, Warsaw is considered that place (saying it's the NY of Poland would be a bit of a stretch, but you get my point). As for the general vibe, Warsaw is the kind of big city you love or hate with a passion, there is no middle ground. You need to learn it and it will be for you what you want it to be. So, whether you're more happy here or there depends on what you are really looking for.

For cheaper city alternatives, I've heard a lot of positives about Wroclaw, but I honestly don't know much about it.

Disclaimer: I'm locally patriotic, but that said I sincerely believe Warsaw is the place to be, YMMV.