Personally, I think it boils down to individual (i.e. the child's personality) and the environment he or she is in, what the child wants and what we as the parents want for the child.
My first child basically only had English enrichment 6 months before PSLE as English was her weakest subject. She ended up with pretty good results (qualified for ESIS and can qualify for any school based on academic merits). However, we (as well as herself) still opted for IP, but not to the 'elite' schools.
These are my observations (just to share):
1. Most students (almost all) have multiple tuitions.
2. Most parents enrol their children for tuition without a clear objective. Many parents are indeed spending a lot on tuition.
3. It is quite true that elite schools have a higher proportion of "rich" parents.
My child is currently in the IP cohort and doing relative well (almost hit max GPA) without any tuition and achieve it independently. My "running" cost for my elder child is almost zero as I invested her scholarship in REITs and the dividends are paying her various fees.
To me, the valuable skills or attributes to be imparted to a child are basically the "survival skills" in life such determination, discipline, resourcefulness, adaptability.
So...in short, I think it is generally correct to say that a lot of money is wasted when parents spend indiscriminately on tuition.