The Baltic republics (Estonia, Latvia and Lithuania) were pretty developed before the Soviet annexation. At first the Soviets were heavy-handed and thus were seen as occupiers. After the WWII the Forest Brothers continued their resistance against the Soviet government for several years with popular support. In the late 1980s the independence movements had much more support in the Baltics than in the other Soviet Republics, with 25% participating in the Baltic Way human chain protest.
The Kremlin must have known about the rebelliousness of the Baltics. It was further amplified by their geographic proximity to the west, the Baltic maritime traffic being a window thereto, and most Estonians illegally watching Finnish TV, which permitted them to see the western way of life. Did the Soviet government try to defuse the resentment and placate the population by allowing them to have higher standards of living? Did the people of the other Soviet republics visiting the Baltics think that it's unfair that they get more consumer goods? Did the Soviet government acknowledge and try to explain these differences?
Along with the Belarusian Economic Region, the Baltic Economic Region suffered the most material and human losses during the years of World War II. This required a much larger investment per capita than in other areas to restore transport and energy infrastructure, communications, and production capacities. In fact, the entire industrial base of the Baltic states was created anew in the post-war years in the USSR. This ensured greater indicators of output and product quality than in other regions of the USSR.
In 1956, the share of the Baltic republics in the income of the Soviet Union was distributed as follows: Lithuania - 1.1%, Latvia - 1.2%, Estonia - 0.7%. At the same time, during 1951–1955, of the total capital investments of the USSR, Lithuania accounted for 0.6%, Latvia - 0.7%, Estonia - 0.7%. These proportions continued in the future (although in the 1970s Lithuania managed to increase its share in the total investment from 0.6 to 1.2, and Latvia from 0.7 to 0.9).
The main components of import from other economic regions were fuel and raw materials: oil products, natural gas, coal, rolled ferrous and non-ferrous metals, industrial timber, lumber, cotton, wool. The local economy was one of the most efficient, and local products were in great demand on the domestic market of the USSR.
In general, the Baltic countries were net donors to the USSR budget.
Sources: Orlowski, Lucjan T., Direct transfers between the former Soviet Union central budget and the republics: Past evidence and current implications; Misiunas, Romuald J., The Baltic States, years of dependence, 1940–1990