One element the other commenters have missed is where the oto is in the purchase cycle.

Let's say you have a membership site for say $20.00 per month to keep the math easy. Good perceived value and people will likely stay on for a few months at least.

But like anything, most customers may not see long term value and your average drop out is after an average of 4 months. So, your average revene expectation is $80.00

By lowering he monthly price (6 months for $90.00 - or $15.00 per month, you increase your profit.) If they do drop out, you made $10.00 more. If they forget it will auto bill at month 6, you capture an extra $90

So, always do a oto when the customer is in the decision stage. Oh = this is a better value for me!

The idea of upselling on a thank you page is great.

But, and the real experts at this are godaddy, they upsell all the way and when you go to pay via clickbank, they open up a billing agreement with a $500.00 monthly limit.

At the thank you page, they show you a multitude of offers. Click OK and the sale is automatic (provided it's below $500.00, which it almost always is) because you just agreed to a paypal billing agreement (vendor initiated billing)

It works like a charm.

Also, you should look into Paypal Micro Payments = A new service for small amounts like $5.00

Paul