[jqm]

Maybe they feel they might need the rocket engines in their inventory at some point.

I think some rocket components were produced in Ukraine, not sure if that applies to this. So maybe they don't want a limited supply diminished.

[seizethecheese]

> I think some rocket components were produced in Ukraine

If true, this is a significant wrinkle in the story.

[trhway]

It is Yuzhmash in Dnipropetrovsk, Ukraine (still, Putin is working on the issue).

http://en.wikipedia.org/wiki/Yuzhnoye_Design_Bureau (search for Antares :)