They come in $20-40 range (also in stainless steel), and are called Hori-Hori (Literal Japanese translation “dig dig”)

http://www.nisaku.co.jp/njc/garden/knife/0650-LeisureKnifeN/0650.html





And here's the big brother, YAMA-KATANA ((n) woodman's hatchet)






Sure looks tempting