How many onions would you use for a curry?

My husband likes to cook curry. An indian friend showed him how he cooks a curry once and now my husband is convinced that onion should be the basis for all curries. When he makes a curry for us he makes about enough for us to eat and freeze whats left over for another meal. He never uses less than 5 big onions and will most likely use 6 or 7! I think he relies too much on the onions for flavour in his curry. He does use spices and makes yummy curries but I'm curious to what others think to his method.