In this case, while I get that the first translation isn’t at all natural in English, it’s really just a matter of expecting a translation to point us in the right direction when it simply doesn’t. Why? Because some things don’t translate, and in the case of English and Japanese, the two languages have such hugely different expressive strategies that it’s not at all uncommon to have to reword and interpret a sentence in order to translate it naturally (i.e. sometimes, you can’t even just stop at matching phrases with equivalents in English; you have to decide on the overall message yourself and write the translation almost as an explanation).
Here, grammatically speaking, 欲しい is an adjective in Japanese. You can’t change that, even if you can translate it using a verb form in English. Like Leebo said, 猫 is the grammatical subject of 欲しい in the Japanese sentence, even if that’s not very natural in English. (Just another example: 好き is an adjective in Japanese; ‘to like’ is a verb in English. The two languages are just structurally very different.)
To be fair, however, Japanese dictionaries don’t list ‘subject particle’ as が’s only function. You’ve also got stuff like ‘marking the target of hope, ability, liking, disliking and so on’.
This is about the nuance conveyed by が, which is an exclusive one. The first sentence is just a comment about Switzerland. The second emphasises the fact that Switzerland (and not any other place) has a high cost of living. If you think about it, even in English, something being the subject of a particular verb/adjective does have similar consequences: ‘John is using the dryer’ likely implies that no one else is using it – or no one else can, at any rate – even if we must admit that this inference is also partly due to the use of ‘the’ before ‘dryer’, which implies there’s only one dryer available.
This is a possible approach, yes, but given how Japanese tends to work, with sentences being parsed as you read them, with modifications to the functions of phrases being made as particles appear (e.g.「これはすごい」is just ‘this is amazing’, but「これはすごいと言った人」is ‘the person who said this is amazing’), well, you could also treat one of those subjects as a ‘sub-subject’. Honestly, I haven’t seen many double-が sentences, so I don’t really think this is something to worry about, but you really can just take it that the statement「物価が高い」applies to「スイス」, and that this is logical because スイス comes first in the sentence, and hence likely influences what comes immediately after it, particularly since it can’t be the subject of anything else. In other words, the sentence ultimately looks something like this:
{スイスが[物価が(高い)]。}
I don’t really know how else to explain it besides saying that you will get a feel for this if you keep observing how the two particles are used in Japanese, and in fact, more often than not, if you insist that it’s a subject particle and then attempt to create an explanation based on that axiom, you’ll find that the end result is a better fit for Japanese grammar than if you had gone with, say, a ‘topic particle’ explanation. There are other things you’ll see, like how most particles have a shorter range of influence within a sentence than は and も, or how most case particles (i.e. が、を、で、に and other particles marking a grammatical function) tend to play their role under the influence of the nearest verb/adjective, but that’s not immediately relevant to this discussion.
Maybe a final thing to think about is this: a very common and simplistic – but nonetheless helpful! – explanation given by Japanese teachers to beginners is that が places emphasis on what comes before it, whereas は places emphasis on what comes after. In that light, the Switzerland example feels more like this:
For further reading, here’s something I translated that based on a book from a Japanese grammarian discussing the five main differences between は and が. (My translation was quite literal, so I’m sorry if it doesn’t read very well…):
PS: I’ve just realised that I should have translated 主格 as ‘[the word in] the nominative case’ for difference (3), and not as ‘the subject’. Oops. Now I see why the authors chose to use 主格 (nominative case) there instead of 主語 (subject). Oh well… sorry about that.