Happiness is derived from believing that you have gained somewhat an advantage over another person. The advantage can be wealth, health, education, marriage etc. Anything that says 哈哈! 我有你沒有 ... brings happiness to the person who asked the question.
You bought a BMW you sibei happy not because the BMW makes you happy. It's the people around you who cannot afford BMW that will make you happy. If everyone owns a BMW in Singapore, you will not be happy. It's the same with Rolex and holidays at exotic destinations etc.
This is why comparing is very important. It's through comparison that you enjoy the advantage that you have gained.
Of course, it's also important to mask your comparison (and eventual gloating) as "concern" 關心. No wonder CNY is the perfect opportunity to showcase your success and whack the losers.