How much individual members make is irrelevant without other core stats to back them up like how many man hours go into supporting the websites each week? how long has the website been run this way? does the site have any other advertising? what market share do you have for your niche? do you rely on return visitors or are you always sourcing new visitors? how much do you spend on promotions? is your site informational or does it sell a good or service frame your question appropriately and I'm sure you'll get much more useful information. After all, a number on it's own will just inspire envy if it doesn't also show the hard work that has gone into getting there.
I would add to add with the number of unique visitors, CTR, etc. Doubt anyone will share their niche if they are making good money