Well, I thought I had this all figured out but apparently not so much. The phase converter must be derated from what I've read for anything above 3hp, which actually seems like for anything 3hp and above and they start getting (as you noted) pretty expensive.

I'm in the territory where it is actually starting to look less expensive to simply buy a rotary converter for the 3hp motor and dump my plans of a 10hp planer and instead get something smaller and single phase.