Proper traditional French mayo is 70-80% oil. Shit mayo from the shop actually has less fat, usually 65% for "full fat" versions and 30-40% for "low calorie" bull shit. Reduced fat content is achieved by adding unnecessary shit like starch. So yeah, mayo, as in real proper mayo, is a whipped oil, not egg.
According to my (parisian) cooking school, they managed to do 70 litres of oil with a single egg yolk while experimenting. Then it became too impractical and they had to stop.