A lower price is useful when both bottles carry the same approval and the same viscosity. Mobil 1 ESP 5W-30 and a Liqui Moly Top Tec 4200 can sit next to each other because both publish BMW LL-04 and VW 504 00. The cheaper one is a real saving.
A cheaper 5W-30 with no maker approval is a different product. It may be fine in an engine that only asks for ACEA C3, and it is the wrong oil where the cap names LL-04 or 504 00. Compare the approval line before the euro price.
Pack size changes the sum too. A 5 litre can at €62.50 is not automatically dearer than a 4 litre can at €49.90. Divide by litres, then decide.