Travelling by bus from Prague to Budapest is usually the cheapest option. But if you are planning to return to Prague, it might be worth checking for discounted return train prices. There are several companies providing transport from Prague to Budapest by bus. Buses are routed via Brno, Bratislava and Györ. Travel time is between seven and eight hours.
Major bus companies operating on this route are Student Agency, Eurolines and Katev Travel.