PPS is not some complicated algorithm. Some programs are unable to do it because it will require capital (if being done honestly), while others choose not to do it.
For instance, here's how rudimentary it is. I checked out a TopBucks site
http://www.herfirstasstomouth.com/s1/index.html
Topbucks pay $35 per signup.
The trial is $9.95 for 7 days, full membership after that period is $39.95. So assuming it goes to full membership, that leaves them with $9.95 + $39.95 - $35 = $14.90
But even if it doesn't go to full membership, note that there is a pre-checked cross sell which reads "Click here to signup for a 1 day trial Membership to Tight Buttholes - One Day Trial Membership for $2.97. After 1 day, Membership renews automatically at $29.97 every 1 month."
So even if the $9.95 trial doesn't go to full $39.95 membership, there is the cross sell safety in place that charges $29.95 after one day. Therefore even if the user doesn't become a full member, but doesn't "Unclick" rather then "Click" to join Tight Buttholes, TopBucks earns $9.95 + $29.95 = $39.99 within one day. And therefore earn $39.99 - $35 = $4.99 in one day. If the user goes to full membership and the One day trial membership goes thru TB earns $39.95 + $4.99 = $44.98 off the member in profit (this is how much earned after paying the affiliate the $35).
A revshare program operating in the same manner can pay $35 or even $70, but not many revshare programs it seems, charge $39.99 for their membership and have a one day prechecked trial of $2.95 trial that leads to a $29.95 membership (Imagine if a site like Karups did this rather than simply charging the $29.95 per month that they do). I'm not quite sure why this is the case. I think it goes back to the difference in the philosophy of their marketing. But even without doing so, we're still in debate as to which one will earn an affiliate more money. I think if Karups included all the features in the join page that a PPS program does, the answer would clearly be revshare.
Revshare programs tend to be quite simple when it comes to price. The price is X for one month recurring. The PPS model hits you with essentially four different subscriptions at once when you're at the join page ($9.95 7 day subscription, $39.99 30 day subscription, $2.95 1 day subscription, $29.95 30 day subscription). Is it wrong to do this? No.
Basically PPS models rely on the fact that many consumers are not keen shoppers. Yes, a certain percentage of them will refund/chargeback, but most will not and the ones that do are made up via other methods such as mailings etc (note the prechecked agreement to receive newsletters on the TB page).
It's reminds of of real world retail, where you buy something for $39.99 that has a $30 rebate. All you have to do is mail in the rebate form to get your $30 so that the product only actually costs you $9.99. I always mail in my rebates, but do any of you know how many people in the general public actually mail in rebates? The number of people is between 1-10 percent and it's usually 1 percent rather than 10 percent. Surprising isn't it? Those are industry figures. Companies understand these figures. They know that rebates work in their favor or they wouldn't offer them. I say good for the company. If the customer doesn't choose to take money back by simply mailing in a form then that's that.
In online adult, companies understand that a certain % of people will upgrade from a trial by choice or default and only a % of those will refund/chargeback. They understand their customers. The difference is that in online adult, these users may be less likely to join other sites in the future even if they don't refund/chargeback the subscription because they realize they may have overpaid. It's perhaps one (and only one) of potentially many reasons why those 'margins' everybody in this thread is talking about have dwindled and continue to get smaller and may very well become unprofitable at some point.