I don't think its value 'has increased faster than an average dwelling in the vicinity': the Pinnacle is very close to the city centre. I live in a shop house around the corner. These are even more expensive. And so are the condos nearby, too.
But in any case, I brought up the Pinnacle as a short-hand for a nice looking HDB, not to say that it's affordable. The city centre is very much not affordable.
You are right that further out, you can get much cheaper flats. Like in almost any city on the planet.