It takes a lot of different things to increase revenues on a website. Two things to help are cross-sells and understanding the customer.
The Prototype.
Consider this real-world example of a sponsor paying $35 PPS.
They have a trial membership at $9.95 for 7 days. It becomes full membership afterward at $39.95. So, assuming the trial becomes a full, the sponsor has $9.95 + $39.95 - $35 = $14.90
If the trial doesn't go to full membership, there is a pre-checked cross sell which reads "Click here to signup for a 1 day trial Membership - One Day Trial Membership for $2.97. After 1 day, Membership renews automatically at $29.97 every 1 month."
If the $9.95 trial doesn't go to full $39.95 membership, there is the cross sell safety in place. It charges $29.95 after one day. Therefore, if the user doesn't become a full member, but doesn't "Unclick" (rather than "Click") to join, the sponsor earns $9.95 + $29.95 = $39.99 within one day. The sponsor earns $39.99 - $35 = $4.99 in one day.
Now, suppose the user goes to full membership and the One day trial membership is still checked. The sponsor earns $39.95 + $4.99 = $44.98 off the member in profit (this is after paying the affiliate the $35).
PPS and Revshare Observations.
A revshare program operating in the same manner pays $35, or even $70. However, not many revshare programs it seems, charge $39.99 for their membership AND have a one day prechecked trial of $2.95 trial, leading to a $29.95 membership.
It is unclear why more websites do not use this approach. It probably is a difference in the philosophy of each sponsor's marketing. However, without considering marketing approaches, there is still no clear-cut answer to which earns the affiliate more money.
If a site included all the features in the join page a PPS program does, the answer would clearly be revshare.
The Mechanics.
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, on the join page. There is the $9.95 7 day subscription, the $39.99 30 day subscription, the $2.95 1 day subscription, and the $29.95 30 day subscription.
Is it wrong to do this? It is up to you to decide.
Basically, PPS models rely on the fact many consumers are not keen shoppers. Yes, a certain percentage of them refund/chargeback, but most do not. For the rest, they are made up via other methods, such as mailings, etc. (note the prechecked agreement to receive newsletters on the sign-up page).
An analogy.
Think of real world retail, where you buy something for $39.99 with a $30 rebate. All you have to do is mail in the rebate form to get $30. In the end, the product actually costs $9.99.
How many people in the general public actually mail in rebates? The number of people is between 1-10 percent. Usually, it is closer to 1 percent, than 10 percent. Surprising, isn't it?
Companies understand these figures. They know rebates work in their favor, or they wouldn't offer them. Good for the company. If the customer chooses to miss out on money back, by simply mailing in a form, then that's that.
Conclusion.
Getting a sponsor program to work is not easy, nor intuitive. It requires using numbers and techniques to exploit user behavior and tendencies.