This is pieced together from the Wikipedia articles on tin foil and aluminum foil. Obviously tin foil was, at one point, cheaper to manufacture than aluminum foil, though that changed. Wikipedia suggest that around 1910, there were already processes to make aluminum foil efficiently, but aluminum foil didn't displace tin foil until after WWII.
What economic factors came about after WWII that made aluminum foil suddenly more attractive than tin foil? Was economics the only consideration?
One big factor was the restructuring of the market. Before WWII, Alcoa was a monopoly maker of aluminum -- it controlled between 1/3 and 100% of the market at the various stages of aluminum production. During WWII, the US government built massive facilities to churn out aluminum for war aircraft production, more than doubling US aluminum production capacity. After WWII, many of these new plants were sold off to Reynolds and Kaiser, giving Alcoa serious competition.
So a combination of increased capacity and competition brought down prices and made much more household aluminum consumption affordable.