The pricing structure for water means that the more you buy the cheaper it is per litre. Nothing new here, the majority of products are priced in a similar fashion, but for water the quantity increase measured against price increase is very steep. It may cost 20% more to get 100% more water. This is why rather than buy 500ml bottles we buy a 1L or 1.5L bottle, which costs not much more for far more water..

When staying in one place for more than a few days we buy 4L or 5L bottles of water and refill a 1.5L bottle from that.

In the Philippines the 1.5L bottle cost P50, the 4L bottle cost P90. 80% increase in price for 400% increase in quantity.