This should be correct too, 'The hotels by the sea are expensive'
My Hungarian girlfriend said that she would rather say: A tenger melletti szállodák drágák.
The hotels by the sea are expensive
And dear = expensive
Why is "tenger" here not in accusative?
The accusative is only used for a direct object. There is no object of any kind in this sentence.
Okay, thank you. [I was confused, in German "the sea" would be an object.]
neben dem Meer -- I see no object at all but rather a prepositional phrase with the dative.
In Hungarian, I think nearly all postpositions take the nominative case.