You get 20 different tickets if you go to 20 different supermarkets. Some regional public transport companies are like aldi or kaufland, cheap, abundant, accessible... Some are like edeka or rewe, expensive. They don't all offer the same level of service and that's one of the reasons prices differ... Another is general economic differences, wages differ too. It's just not that easy to streamline it EU-wide if a Bulgarian average paycheck is 861 € and a German one is 2741 €. Too government supported and you get 100's of empty busses driving noone to nowhere. Too much free market and there's no service at all on non-profitable routes. Organising good public transport in a good, financially durable way, isn't as easy as it seems. Tickets like the 49 € are awesome, but also risk off-balancing the public transport finances.