From my understanding, they think it is affordable then I have no obligation to save money for them. If I buy one $5000 suit to save money, they won't give me the rest $13000 to spend on something else.
I'll disagree on this. In my opinion, you shouldn't make your parents spend much more money when there is almost no reason to. A good (MTM) suit from something like Spier and Mackay would most definitely be enough for you. But yeah, if your parents are multimillionaires and they really don't care, go for it.