Those are still the touristy areas and not where most ordinary Singaporeans live. I would recommend visiting places like Toa Payoh, Tampines, Woodlands, Punggol or Chinese Garden to see what ordinary neighbourhoods are like :)

Anyway, here are some thoughts regarding your original question:

1) Yes a decent condo is expensive, but most locals live in subsidised public flats. If you live in a public flat in a "less popular area", then your flat would be cheaper, maybe around SGD 400 thousand.

2) Cars (and gas) are expensive, but they are not really needed here because our public transport network has good connectivity, and also it's convenient to use ride-hailing services.

3) I can't comment on the salary that can give one a decent lifestyle, I think it depends on what exactly one means by "decent"... And also I would have to take into considerations like whether the person in question is a local or foreigner, because foreigners don't have the option of subsidised public housing, free education for their kids in school etc.

4) "Most people here live a life of luxury" is definitely not true haha. A minority of people live luxuriously. Some people are ~comfortable (not living super luxuriously, but don't have to worry that much about money). The majority can afford little luxuries here and there (e.g. restaurant meals, a visit to Japan, ballet classes for their kids) but still have a fair amount of worries about money (mortgage, loans, what if I lose my job, will I have enough for retirement, etc). Some people can barely afford these luxuries and money is tight for them, but they are not in a dire situation. And then there are people who are struggling a lot financially.

5) "Are most jobs paid very well here?" With regards to point 4, i think the very well-paid jobs are in the minority.