Upvote:1
http://www.euroticket.pl/en/index.php
here you can find bus tickets, it takes around 9 hrs of travel and costs around 50-60 EUR
Upvote:2
I just checked the German railway site and found several options for under €40 on 11-11-2015. I think that with that kind of prices it is not worth breaking the ticket unless you want to break the travel.
If you want to buy a ticket all in Poland, I think this is the site to use. But there might be other/better options, I never used the site.