This may seem like a ridiculous price-proposition. For € 1,50 you get half a liter of Spa Blue (non-sparkling mineral water) and for half the price you get three times that amount of water. This indeed seems ridiculous, until you hear that you find these prices at gas stations and railway-station mini-supermarkets. And at those locations the value of a bottle of water that you can carry around easily and can stuff into your bag is higher than that of higher volume bottle. So here, ease of use is valued over content. Which means the value of usability is: (half a liter in a half-liter bottle) - (half a liter in a 1,5 liter bottle) = €1,50 - €0,25  = €1,25 per half liter.

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