Krakow in Poland is amazing. Beautiful city with much history and beautiful churches and buildings and also good and cheap shopping. The food is also good and cheap. Viapano a meal and a drink costs about 5 euros and a pack of cigarettes costs about 2 euros. In Krakow you can visit Schindlers factory, the jewish ghetto and other cool stuff. You can also visit the concentration camp Auschwiz-Birkenau only an hour car drive away, there are also cheap trains. Transfer from the airport with bus or train is about 1-2 euros. Hotels can also be really cheap.
Prag is also a really nice city if you are looking for a cheap one. When you're in Prag it feels like you're in a fairytale because it's so pretty
I would add St. Petersburg, Russia, to the list. Although it's not in Europe it's only 200 km from Finland and Estonia. The city center has a lot of palaces and churches and almost all houses are more than one century old. There is a network of canals in the city center and the metro is the most beautiful in the world. The prices are about 2/3 cheaper than in Western Europe.
Try Lisbon or Porto, in Portugal. It's cheap and beautiful and safe and lively, fine weather is the rule, fine beaches are just around the corner, summer festivals happen almost every weekend, and there are cheap flights from many destinations. Cup of coffee espresso: 0,65 euros average. One beer: 1 to 1,50
