I was able to book a first class seats on Railjet from BUD-VIE after registering.
Yes the 2Class is horrifying.
From Vienna, took the train to Bratislava and just bought tickets at the station
Beware! DONT Book the Bratislava Ticket from Vienna!!!
Wien - Bratislava 16,-
VS.
Siebenbrunn-Leopoldsdorf - Bratislava 7,-
+ 1x Zone "VOR" 2,20€
+ 1x Zone "VOR" 2,20€ (if you drive back)
----------------------------------------------------
11,40€!!!
BEWARE 2 YOU NEED A TICKET FOR THE BUS, TRAM, UNDERGROUND LINE IN VIENNA!
THE ARE
NOT INCLUDE!
(So in addition you have to count to the 11,40€ a Ticket for Vienna to from/ to the Hotel but you need it for the 16€ Ticket to.)