i did a search on abebooks and found 4 copies...
2 in the U.K. at dancing goat books in Norfolk,
one in New York and one in VT. $22 - $75 dollars.

1. ROBERTS John S (compiled & edited by): The Legendary Ballads of England and Scotland (Frederick Warne [Chandos Classics] no date). Presents texts only - ie, no music - for a a good selection of traditional ballads, the result being similar to Percy's "Reliques". One of the Chandos Classics poetry series in brown binding, title colophons in gilt on front and spine, the latter being somewhat darkened. A little fraying at head. A couple of brown streaks appear at edge of first few pages, but overall quite clean for its evident age. Bookseller Inventory #7194
Price: US$ 22.04 (Convert Currency) Bookseller: The Dancing Goat Bookshop, Norfolk, NFK, United Kingdom (Search this Seller's Books)(Ask Bookseller a Question) Add to Basket Book Details

2. ROBERTS John S (compiled & edited by): The Legendary Ballads of England and Scotland Frederick Warne 1887). [Text only + short introductory notes to a collection of mainly traditional ballads].Plain green boards with some spotting on rear; spine dull with wear at head, foot and centre (where an abrasion occurs). Title colophon scuffed. Front hinge weak. Bookseller Inventory #6388
Price: US$ 27.55 (Convert Currency) Bookseller: The Dancing Goat Bookshop, Norfolk, NFK, United Kingdom (Search this Seller's Books)(Ask Bookseller a Question) Add to Basket Book Details

3. Roberts, John S. THE LEGENDARY BALLADS OF ENGLAND AND SCOTLAND London 1887. Sm.8vo., 626pp. Good, cover soiled, some wear. Bookseller Inventory #a26591
Price: US$ 45.00 (Convert Currency) Bookseller: Xerxes Books, Glen Head, NY, U.S.A. (Search this Seller's Books)(Ask Bookseller a Question) Add to Basket Book Details

4. Roberts, John S., editor. LEGENDARY BALLADS OF ENGLAND AND SCOTLAND, THE London: Frederick Warne & Co. Cloth. Good/No jacket. 12mo - over 6¾" - 7¾" tall. 628pp. N.D. Inscription is dated 1887. The "Chandos Classics" is noted on the title page. Texts only. Rich collection of ballads; editor expresses gratitude to Prof. Child for his work in collecting, and many others in addition to the numbered ballads. Spine and edges of boards yellowed; some chipping and corner wear. Hinge cracked but intact, with a few tears. Bookseller Inventory #6667
Price: US$ 75.00 (Convert Currency) Bookseller: Country Bookshop [Member VABA], Plainfield, VT, U.S.A. (Search this Seller's Books)(Ask Bookseller a Question)