It's not that they're exploited. Cambodia's economy is just really, really inefficient. Food prices in Cambodia are really high (ep 4), higher even than in Berlin [0] by 21%, not to mention Eastern Europe (2+ times Warsaw's prices, 4x if you shop around).
The sad thing is, the wages in sweatshops won't go up much. Sooner or later automation will advance to the point where even $3/day for sewing garments will be too high and they will all be fired.
with regards to the numbeo figures: these are pretty offset by the high price of Milk, Bread, Cheese, Apples, Wine - all of which are non-native foods and would have to be imported to Cambodia (and which wouldn't be part of an average diet there). In fact, most of the foods there are non-native - potatoes? No-one's eating these either.
Local food types (rice, noodles, veg, SE Asian fruits) are ridiculously cheap in Cambodia, though could still very well be expensive in comparison to the wages..
edit: reading further, I'm not sure they've sourced those figures well at all, they don't ring true. 0.43€ for a bottle of water? Come on, that's nowhere near the local price unless you're buying it at your western hotel
Nitpick: Because Cambodia was part of French Indochina, bread (specifically baguette bread) is in fact an everyday staple food to Cambodians, at least in the cities.
[0] http://www.numbeo.com/cost-of-living/compare_cities.jsp?coun...