Loomis House Press have recently issued a reprint of The Traditional Tunes of the Child Ballads at $39 us papaerback and $49 us hard cover - plus postage. They are slightly reduced in size from the originals but I find that no problem myself. I had purchase a used copy of volume 2 for about $170 can so to pick up the other three for $190 cananian was not a problem. (Personally I felt that one volume of the full set was better than getting the Singing Tradition which didnt seem to give me much choice of tune. It should always be remembered that Bronsons interest was in the tunes and that great versions of the words exist elsewhere.)
For some reason the price of The Singing Tradition has dropped considerably recently, I see a paperback copy for less that $30 us. Though I wonder if the introduction, which is better than that in The Traditional Tunes is worth that.