I'm somewhat surprised by the price of the 3D printed lugs.

I've had a few things 3D printed in a material they call "stainless steel" and they were pretty reasonable. Much smaller, to be sure: a couple saddle badges (about $10) and one part for a Resilion brake (about $25). I had them "printed" by Shapeways.
According to the Shapeways website,
"Steel is printed by depositing a liquid binder onto a bed of steel powder one layer at a time. The product is then removed from the printer and infused with bronze. While the product is being transferred from the printer to the infusion chamber, it exists in a delicate "green state" which does not support interlocking parts." I'm not sure I'd call that "steel" but they do. So I guess your lugs would be "printed" by a different process? When Shapeways "prints" brass or bronze, they actually print a wax model that is then used for a lost wax casting.

I wonder if a "green state" print of a lug would be sturdy enough to be assembled into a bicycle frame. Brazing would (could?) then infuse the brass into the steel. I suspect this process, if it would work at all, would be different enough from conventional brazing that you might as well just learn to do it yourself.