We're pretty lucky in Australia as most of our direct ancestors came out during the 19th century.  However, for the 4 direct ancestor families, i bit the bullet and bought them - luckily with a 10% discount.  Then I immediately emailed the scans to all the relevant researchers with the request that they pass them on to others.  I'm hoping that perhaps I'll get others that are not direct ancestors, but other family members in return at some stage.