Re: This is why you need the GPL...
No, the point of the public domain is that anyone can use it in any way they want, including producing a "closed"/"proprietary" derivative product -- eg the film version of Sleepy Hollow with Johnny Depp. Just because it's based on a public domain work, doesn't make it a public domain work.
Eicher's article falls on its face when it chastises the small publisher for profiting from public domain works -- isn't the point of the public domain that anyone can do what they like from it -- and as others have said, many of these books have actually been retypeset to provide a clean, modern, legible version rather than the grubby scans and flaky OCR coming off Google's virtual presses. The high price is not just about having a monopoly, but is an attempt to offset the cost of that typesetting against the small number of customers.