Each Zebu cow is probably worth as much as the house that they live under.
Zebu provide milk, and from their dung comes both fertiliser and fuel. If the owner is lucky, perhaps there will be a calf or 2 to sell, and later, the cows are fattened, slaughtered and sold for beef. (Although, Cambodian beef is generally tough compared to that of Australia or New Zealand)) The hide is also sold, tanned and used in leather goods.
Although Zebu look seriously thin, as I understand it they are well-looked after and generally healthy. (They are too valuable to treat in any other way)