Many years ago, HDB flats were sold cheap because they were sold at real cost subsidies. Resale flats will surely be more expensive as they are better than the intiial selling price.
However, if HDB stuck to cost subsidy, the new flats will still be sold at the cheap prices, and the resale flats THEN will be higher by a bit.
Scenario 1 (HDB uses real cost subsidy).
Assume three areas, A, B and C. A is built at Year 0, B is built at Year 5 and C is built at Year 10; A is located in the best space (say Toa Payoh) since that time got land, B is build further out (since land is slowly runnig out; say Ang Mo Kio and C even further out (Say Woodlands)
At Year 0, HDB builds and sells new Flats at A for $100,000.
At Year 5, Flats at A are now worth S$150,000 and HDB starts building new flats at B for S$100,000 (discounting inflation for the purposes of more easily illustrating this point).
At Year 10, HDB builds new flats at C for S$100,000 still. Flats at A are now worth S$200,000 and Flats at B are now worth S$150,000 (due to property price appreciations since A is now better than B and B is better than C).
Now look at the market subsidy situation:
Scenario 2 (HDB uses market subsidy)
At Year 0, HDB builds and sells new Flats at A for $100,000.
At Year 5, Resale Flats at A are now worth S$150,000 and HDB starts building new flats at B. But instead of selling at a real cost subsidy of 10,000, HDB now sells it at S$140,000, citing that resale flats are worth S$150,000 and now gives the market subsidy of S$10,000.
At Year 10, By this time, resale flats at B will have risen from 140,000 and at A even more. A knows that since new flats at B are 140,000; he can ask for higher. Hence A's price appreciates to say, 225,000 and B's resale price is say, 200,000.
Now, HDB builds new flats at C. Using market subsidy again, it then discounts the current resale price of B and says, since B is 200,000, my new flats at C are now S$190,000 (even though cost is still 100,000).
Can you now see the difference of how market subsidy is propping up the market? At the same time, the HDB tells you "B and A, aren't you glad your property prices are increasing?"
Now multiply this by a factor of X, and you can see where this is headed.
With the rise in HDB new flats, propping up resale flats price; the private properties also will increase in price (because the resale flats prop up their price). Now who do you think gains the most from private properties prices going up?
The everyday Joe like you and me? Or the very rich who has the money to buy 10 private properties at a go for investment?
To answer your last question, why don't you try comparing the price of a new flat in Tanjong Pagar in the 1970s compared with the price of a new flat in say, Punggol (super ulu place). Even taking into account inflation, you will see the Punggol new flat is far far far more expensive.
Not sure if I'm right....
But many years ago.... Govt was try hard to get S'poreans to move from Kampong to modern highrise housing so as to make better use of the land. Thats why to ensure S'porean are willing to move.... flats are sold 'Cheap'... but at the same time, RESALE is also cheap.
But as more and more S'porean get used to the idea of Highrise living.... and begin to sell their smaller unit to upgrade to bigger ones... It does seems that a common citizen could now make $$$$ on his/her property. Therefore 'Market' demand will take over. Therefore if the 'Market' seems to think my flat is worth $300K.... no way I'm going to sell it for less then $295K.
But the question of why even new flats are price so high....
I admit that I didn't do any research.... but I believe its location location location..... While a newly built 3Room in Woodlands is around $120-$185K (depending on levels).... I believe the 50 storey one at Tanjor Pager (hope I spell it right :sweat

cost alot more.