Extruder is easy to build now is probably the best machine to build as first, since it alone can replace wire mill, lathe, and plate bender - at same material cost per produced item. And in addition to above it can also do things no other machine can. It's pretty much the same as IC2 metal former - all in one machine, without any cons. Previous GT extruder high tier machine.
And for some reason lathe produces less rods then extruder and costs diamond to construct. Any reason to build it?