So this review is going to be broadly positive about IE hence will be dismised by some as sponsored promotion - it's not. I'm a male from London who's been using IE on and off over the last 4 years. Negatives first: it is indeed expensive; the attempts to hook you in after creating a profile (but before paying up) by random obviously system-generated hellos from specious profiles is extremely annoying (but you learn to ignore these and it does seem to have eased up thankfully of late); the time-pressure on male members to secure a date/relationship within the fee window skews the playing field; and the membership claims are obviously wildly inflated (I agree that the active membership at any one time can be numbered in the hundreds not thousands).
All that said...I have had 5 paid memberships on IE at 6-9 month intervals since 2013. On every one of these I have had several "dates" following correspondence on the site and on every one also I have entered into at least one physical relationship, typically more than one. Of course not every correspondence leads anywhere, any more than on any other dating/adult site, and again as everywhere else it's a "seller's" market for women. But from my expeience, if you compose an engaging profile, write a decent email (tailored to the recipient, not cut and paste) and are prepared to cast your net widely IE does in fact work. (If you're outside a metropolitan area, as others have noted, it's ound to be more difficult.)
Also, final note: unlike Ashley Madison (and we all know what happened there!), IE allows anonymous cash payments which given the nature of the site is a considerable plus.
High if limited quality of members; discreet and functional.
Expensive (for men); gender imbalance; some fake/spam profiles.
Michael does recommend Illicit Encounters to friends/family