According to http://www.opengroup.com/mubooks/185/1851826858.shtml , Pádraigín Ní Uallacháin's new book Amhráin Oirialla - Songs of a Hidden Ulster Published by Four Courts Press (ISBN: 1851826858) costs $126!
It's a 450 hardback book with illustrations and Audio CD (according to notes with the Dealg Óir album, there are 2 CDs containing 54 songs sung unaccompanied). An Dealg Óir, issued by Gael-Linn, contains a smaller selection of the songs from the book, sung with musical accompaniment.