Upsell Paypal/Wordpress/Whatever
So I'm asking this... without using Clickbank, Infusionsoft or any other "expensive" solution. I know there are a number of paid plugins like the ones of Easy Digital Downloads among others.
I hope you can share your experience implementing this kind of systems without killing conversions.
The most sensible solution I found is to create a link tree with several paypal buttons depending on the branch taken by the buyer.