I also liked the portability of the design myself. The cost is adding up quick but I think I'll still be close to the same cost to a manual entry level bender by the time I'm done. You are correct in that the dies are expensive by themselves. This unit is designed to use the Pro-105 die sets from pro tools
http://www.pro-tools.com/. There is a guy on minibuggy.net occasionally making die sets for sale.
Investment to date;
$18 : Plans
$85 : Air/Hydraulic Ram @ Harbor Freight
$60 : Bushings(Plans give the details so this is not needed if you have a lathe and
can make yourself)
$100 : Steel (Could be less or more depending on what you can get at salvage cost)
$50 : Misc Hardware & Hardened Shafts