Go through your results for flights to Koblenz in Germany with Netflights.
If these flights are too expensive, try searching for a different time of year. It's likely that prices for both flights and accommodation So if your dates are flexible, consider looking at different times of year.
So, if the flights to Koblenz don't work for you, you could always try searching for flights to other airports in Germany.
You can also broaden your search by looking at more than one departure airport. Have a look around – you might be able to save by flying from a different airport or city.