To begin with, there is a double system of payment and prices. Cubans must pay in their currency to buy in stores; that is, in pesos for Cubans. While tourists pay in Convertible Pesos (CUC) and tourists can only buy in dollar stores.
Regarding daily life in Havana, you have to know that the average Cuban salary is about 350-400 pesos. One CUC convertible peso is equivalent to 1 US dollar or 24 pesos to one dollar. Some people work for less in stores or museums. There are dentists who earn as little as $ 12 a month. A taxi driver can earn more money than a doctor. The pension is between 3 and 8 dollars per month. Among the best paid are the Police, between the National Peso 2500-3000 (= $ 150 per month)
Of course, this is not all, to estimate the cost of living in Havana you have to take into account the cost of housing, electricity, water, and these costs are very low in Cuba.
Second are social benefits, with the ration brochure (the booklet) that is given to each Cuban family for a basic ration of basic foods such as rice, beans, oil, salt, sugar, and bread. The following also comes out in limited quantities: 1 bar of soap, 1 toothbrush, and 1 tube of toothpaste. Milk is only available to mothers with children under the age of six.
For many families this ration is only enough for an additional 15 - 20 days for which food must be purchased. However, no one dies of food shortage, but for a large number of Cubans meat or chicken is a luxury. For the elderly and single mothers life in Havana can be difficult and they have a hard time fulfilling the purposes.