Google is the ONLY site you could even get close to the numbers you are talking about.
I have a listing of the top 400 sex search terms on Google.
According to Google - these get a total of almost exactly 2 million searches a day. However - the number is much lower - as google reports:
teen sex= sex teen = teen sex pics.
The reason Google is the only place you can get decent traffic is that all the other search engines put sponsored listings first. The difference between a number 1 and number 2 listing is huge. 1 and 5 is even bigger.
I have the top listing for about 40 of these already. I know how much traffic each of these gets by extrapolation. If I had the top listing for all 400 terms I would get about 200-400K a day is my guess.
The top 150 would be closer to 100 - 200K a day - IF YOU WERE #1. #5 would be closer to 20-40K. That would be about 600-800K a month. If you could get listed in the top 5 for all of them.
If you know antthing about google - you will know that they will eventually delete your pages if they are all forwarding to somewhere else. You may get away with it for a litttle while and !216.239 will only take you so far.
However, if you did know anything about google - you would know that submitting it is useless. But you may have been using submit in the generic sense - so I will let it slide
You obviously don't have the sites up yet - if you did you wouldn't need to ask. I know all the people that do have multiple good listings (not all by name, but at least by design) and I am pretty sure they would tell you the same thing. The one guy I do know that also does it does well, but no where near 5,000 sign ups a month.
I know lots of "professional SEOs". They are people that get paid to list other peoples sites high. If they could really do this on competitive terms - they would have been doing adult a long time ago. I can count the number of people that know google well enough to do this on two hands. It doesn't take them 6 months either.
Good luck, and to answer your question - depending on the keywords - anywhere between 80 - 1500:1.
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