Hi Linda,
1st of all check the contents & the ingredient of the milk.
If u notice, most of the milk tin have a chart to tell the consumers the amt of minerals and vitamin that the milk powder contains.
There is another small corner of the tin that stating the ingredients eg palm oil, vegetable oil etc etc..
There may be some slight different in them.
As for the price, it was partly due to the places it was packed, the QC ad QA of the product.
Like Dumex or Neslac, they are packed in msia or Indonesia or Asia country where labour cost is low, QA & QC varies. Thus, the price are different.
GainIO and Enfalac series may pack in western countries and ship over to Singapore so the price are generally higher. It is also belief that they QA and QC are more stingent.