If it's too good to be true then it probably is.
Building a domestic airline network in Poland is a long term investment. You need to alter the way people think. When people want to get from A to B their first thought has to be - I'll fly. Business people have to build their businesses around the ability to fly. People have to schedule their holidays around the ability to fly. People have to search for jobs in different cities based on the ability to commute regularly by plane.
Dumping price promotions will attract a lot of curious people. But that, of course, is not sustainable.
Anyway - the future for Poland is - IMHO - rail anyway. Much like France or Germany.