and some in area, there is lower salary than that,lets say people work for small business man, they will pay you about 50-70$ in a month and the worse is no free day in a week, that mean we should work 7day/week.
Do you mean they get 50$-70$ monthly with no free day every week? I just know this, as far as I know I never found this in my area. I think it is too severe, 50$-70$ monthly doesn't deserve for the payment of full week jobs. 
In terms of US dollars, the standard price of a meal in my country is around $1.5 for food and $0.5 for drinks, but the price can vary depending on which city you are in, because in our country, each region has different food costs.
I think there is no standard prices of food or drinks. It is just the average price for common foods or drinks. However, food $1.5 and drinks $0.5 are still quite affordable. But I assume it is not in the big city, it should more expensive for the prices of common foods or drinks in a big city.