One post a week from 7 people is way more valuable a network than 1 a day from 1 person.
"Posting" isn't where the value of the network lies. What matters is how many active users there are so that the content/site/network can be monetized.
But if we're talking specifically about the value of particular users or content, then it's all subjective. And one user who posts popular/subjectively good quality posts every day can absolutely be more valuable to a network than seven users who drop a blurry photo once a week and have no followers.
I agree about posting. Activity is most important. Reading voting commenting and posting. Posting is probably the least valuable activity unless it leads to the others.
My point was that content that is sorted into best and worst by 70k users where they login once a week is more valuable than 10k who login every day.