Oh, yes, it seems it is worth buying the tickets for 800 HUF and climb the so many stairs.
If you had enough of the water and sunshine of your Balaton beach, we can recommend an alternative program for you.
Szigliget is a pretty village on the northwest shore of the lake with nice green surroundings and a castle on the top of the hill.
Although the castle itself is in ruin, it is reconstructed and looked after well, offers some exhibitions and programs.
But the main point is the view that you get if you climb up the stairs to the walls and lookouts.
While this small workout will do you good, the panorama includes something really charming.
Apart from the view of Balaton you can see the landscape north to the lake (Balaton Upland), which looks typically Transdanubian and unusual as well, as if you were in a fantasy movie.
The castles website with the actual ticket prices is here.