The profitability of milk production is determined by the production volume on a farm, pricing, and incurred costs. The production volume directly corresponds to the milk-yield level of cows and herd size. These factors are characterised by a positive interrelation. The study reveals that an increase in the milk yield of cows stimulates income growth and, despite the higher costs of animal upkeep, it is connected with a more efficient usage of the workforce. Higher costs stem primarily from the introduction of highly-productive (genetically potent) specimens into the herd, and higher production intensity. The study revealed that the improvement in the milk yield of cows was related to a considerably larger proportion of purchased concentrate feeds in the animals’ feed ration, with a marked predomination of concentrates and compound feeds. In bulk feed, on the other hand, the highest proportion comprised silage and hay silage. Such feed facilitated an improvement in cow milk yield and also had a positive impact on milk production profitability. The growing volume of milk produced on a farm was accompanied by an increase in its price. As a consequence, the economic performance of milk production in holdings comprising fairly large herds of cows (around 30 cows) of high milk yield (approximately 7000 litres) was significantly more favourable than that of holdings with smaller herds and lower milk yield.