“Living standards” includes things like access to the sea and better weather.

Not everyone cares about having access to the urban amenities that Vienna has. Split is also a pretty nice place, even off-season (I once lived there for 3 months February-April.)

That is why the costs of living between the two are not as disparate as you might expect.

Yes but you can also live in other cities in Europe on the coast with similar or lower prices and different tradeoffs. This is my entire point - this was not the case a few years ago - I would say all the comparable coastal regions in the EU were more expensive.