[Dior]

I don't think there were millions or hundreds of thousands at all. At the battle of the 5 armies Thranduil only brought out less than 2 thousand elves as stated in the Hobbit and the Atlas of Middle Earth, and he must have pretty much used most of his warriors. Also, if in the first age, at the time of the elves dominance, Gondolin, which was the greatest elven city, could only turn out 10,000 elves for the Fifth Battle, than the rest of the elven cities must've not contained more than 20,000 elves, and thats in the time of their dominance.