I wish I could but there is too few EC projects for me to give you a good comparison. There a hiatus in EC launches fro 2008 till 2013(prive). Not forgetting that 2008 was financial crisis and I am unable to dig up such old data.
Prive is the only EC we can refer to in PK/SK that topped and finished MOP in the last decade. The resale price of Prive EC is the same as any other PC in PG/SK. Therefore, I think we can compare Sumang EC with any other resale punggol condos which are going for $1,050 on avg.
However, in 2014/2015 when those ECs were sold for $800psf ... ... ... there are no new condos in punggol to compare with at all. So, only data we can use for comparison is the discount from private condo launch.. and that discount now is a far cry from in the past...