Cost of living in Kaunas (Lithuania) is 23% cheaper than in Zaragoza (Spain)
This comparison is lacking data. It provides a decent comparison, but it is not yet reliable. It is based on 247 prices entered by 29 different people.
For example, to keep the same standard of living that would require €2,100 in Zaragoza you would need to make just about €1,626 in Kaunas.