As in any other country, prices in the USSR depended on many factors. However, due to the planned economy and the lack of market competition, prices for goods were fixed and controlled by the state. On average, a salary in the USSR was about 100-150 rubles per month, and food products usually cost a few kopecks per kilogram or liter. However, exotic goods, such as foreign cars or electronics, could cost hundreds and thousands of rubles.
As an example, here are a few specific prices that I remember myself.
Black bread – 20 kopecks.
Pastries (tartlet, eclair, shortbread) – all for 20 kopecks.
Cooked sausage in a co-op store is 10 rubles per kg. In Moscow you could get it for 2-20. I haven’t seen it at such a price here.
A box of matches – 1 kopeck.
Druzhba cheese – 14 kopecks.
Travel around the city by bus costs 5 kopecks.
I might have mixed up some of the prices – I’m writing from memory without searching the Internet.