A better question would be, why would a newly marry couple/1st time buyer/anyone else, who can't afford 200-300K, still die die also want to buy Resale flats in mature estate ?? Its like getting a office in the heart of CBD and wanting the rent to cost no more than in the Heartlands.
A word of advice.... there are cheaper flats in S'pore.... but they are mostly in NEW estate or in slightly more Ulu area.... a friend of my just downpayment his BTO unit (3Rooms) next to S'pore Sport School in Woodlands for $120+K. He will be getting his 'Keys' in 2-3 years time. If you can't wait.... 4Rooms flats are selling between $240-300K in Woodlands.... instead of the same amount for a 3Room flat in AMK, Yishun.
We can't have our cakes and eat it.... If you can afford it, buy where you want, how big you want..... if you can't, then make do with what you can afford.