My price comparison was pretty pointless as I forgot the copper equivalent. [Linked Image]

A 1.5 mm2 Cu wire is about 50% more expensive than the 2.5 mm2 Al. If you compare 16 mm2 Cu vs. 25 mm2 Al, it's 100% more expensive. The difference will be smaller if you compare cables with an outer sheat, since the insulation adds to the cost.