Same floor flat different price

Brother wanted to buy a 4 rm flat next to another brother but found price increased by $84k. It was $280k a year ago when his brother bought it from HDB. It is now $364k from HDB. This is reported in the New Paper.

The price has gone up as it is marked according to market resale value of flats in the area. And this brother is unhappy. He found it unreasonable as the costs of building the two