To my knowledge, there is not a post/poll about the total value of e4 members’ collections. People will have varying comfortability with sharing that number, if they know it at all.
There’s also a lot of variance around those calculations. For example, how does an error collector value their collection? The errors are worth what people are willing to pay. Same goes for trophies, specific promos, and other niche items.
If I had to guess with absolutely no evidence at all, I would say that the “average” e4 collection is worth around $20,000. 