update4:
new bus companies and bus search engine Flixbus , Fernbusse and Aldi-Fernbuslinien are new to me, so I'll share this here.bus search engine: busliniensuche DeinBus.de is a another alternative.
Bus transport is going to get bigger in Germany since there is no more monopoly to long-distance travel from Deutsche Bahn.
I read they even want to start their own Bus connections.
Though that's not bus-related but I'll post it anyway.
Ltur offers one way tickets prior 7 days to the departure from 25€.
Also every week is a special European destination from 35€ one way.
That takes effect on the high speed trains (ICE).
If time isn't your problem or you are in a bigger group you can travel cheaply to the whole country by using the regional trains everything explained on their homepage .
travel.stackexchange.com/users/3411/greg121
You could try BerlinLinienBus .
It's a company for cheap bus lines operated by DB.
Eurolines also have domestic lines.
travel.stackexchange.com/users/2509/gerrit
The cheapest way to travel in Germany is actually to get a ride.
Take a look at mitfahrgelegenheit.de or mitfahrzentrale.de/ .
The trip will cost about 30€ - you just share the fuel costs
travel.stackexchange.com/users/2560/Dirty-flow
At the moment, the best way to find a cheap bus service is the Busliniensuche search service.
It currently offers a search function across 57 companies running one or more bus lines, and all the ones that greg121 and gerrit mentioned are included there.
travel.stackexchange.com/users/961/takrl
Germany is not Hungary.
Labour Costs in Germany are higher than in Hungary.
So don't expect that the bus tickets are the same price.
Hungary is not a good benchmark for Germany.
It is definitely possible to find train tickets for less than 100 EUR between Munich and Berlin.
I can point you to what I have written elsewhere : The strategy to find a "cheap" ticket, for IC or ICE trains, is the same as if you are looking for "cheap" flight tickets.
The earlier you book the more chances you have to make a good deal.
Moreover, avoid peak times, like Friday evening or Sunday evening.
In the past I have made some good deals on Wednesdays ...
Flexibility pays off.
Also check the DB's search engine for saver fares .
If you travel frequently, you might consider to buy a Bahncard .
This entitles you to discounted fares, as well as other advantages.
But it is possible to travel cheaper by train.
From Monday to Friday you can travel on a so-called " Quer durchs Land Ticket ".
And on the weekends you can use a " Schönes Wochenende Ticket ".
These tickets costs 44 EUR and 42 EUR for one person.
If you are more than one person, the price per person is highly digressive.
In the most extreme case, if you are 5 and you travel on a weekend, you end up by paying 8.40 EUR per person!
With these tickets you can travel all over Germany in regional and local trains.
You cannot use IC, EC, or ICE trains.
From Berlin to Munich will take you 10 to 11 hours.
That's almost the double of the travel time of an ICE train.
But, it's pretty close to the duration of a bus trip.
travel.stackexchange.com/users/11860/Maître Peseur
www.klickbus.de offers cheap tickets from Munich to Berlin.
I booked there my trip to the Oktoberfest last week.
Price was something like 20€
travel.stackexchange.com/users/20640/Klara
I found a website where you can compare the respective providers of bus connections.
travel.stackexchange.com/users/7372/Markus87
If train travel is still an option, apparently if your destination (and perhaps also where you start from) is not in Germany then the train tickets costs a lot less.
It was mentioned on the news
and we tried out such a search on the Deutsche Bahn website
and it was the case.
travel.stackexchange.com/users/8068/Jane
Are there any cheap bus lines inside Germany? Something like  Orangeways ?  I've checked Deutsche Bahn cost for transport from Berlin to München and I was shocked with the price about 100 Euro. By Orangeways similar distance costs about 20 Euro... Is there any operator that allows to travel in Germany with so attractive prices?
Cheap bus lines in Germany, something like Orangeways?
travel.stackexchange.com
<budget><buses><germany>
travel.stackexchange.com/questions/8458
travel.stackexchange.com/users/2637/Stepan Vihor
BerlinLinienBus, Eurolines and Klikbus offer cheap tickets from Munich to Berlin, or you could take the cheapest option and get a ride. There are a number of bus companies in Germany with long distance routes, including Eurolines. However, the cheapest method of travel in Germany is getting a ride.
There are a number of bus companies that serve long distance destinations in Germany, including Eurolines.  The cheapest method of travel in Germany is getting a ride.