On amazon.ca setting the price from low to high turned up the AmazonClassics edition of
The Autobiography of Benjamin Franklin as the first hit.
On the other hand finding a good copy of
The Wizard of Oz or one of the Narnia books (out of copyright in Canada) might be a problem although sorting by price would at least garner you freebies first.
And I once picked up a free copy of some of C.S. Lewis's books through Amazon (they hadn't yet been added to fadedpage) and discovered that the publisher had added their own footnotes stating where they disagreed with Lewis.
I must admit that they had ensured that their commentary was easily distinguished from Lewis's work and none of his writing had been modified but it does point out that there is more than bad formatting to beware of.