I think PPS is a completely viable program option.
You don't even have to complicate matters, estimate everything conservatively and throw out any extra revenue that isnt from your membership price (cross-sales, upsells, etc...)
Let's say you charge 24.95/mth and your average member rebills twice.
24.95 x 3 x 0.85 (we'll take off 15% processing fees to be conservative, this can be 5%-10% though)
1 average member = $63.63 in revenue
If you offer $25-$40 PPS you still have enough for you which should easily cover the bandwidth fees and any potential refunds/chargebacks that are incurred, while making profit.
Add in the revenue from the extras and that's a bonus
For sites with very low rebills, unless they make a killing on the extras, they are probably the only ones who have to worry about offering high PPS payouts
