Fabrication of parts to near-net dimensions in a vacuum chamber, followed by grinding or electro-polishing to finished tolerances, is an expensive way to build. The size of vacuum chambers, and the time required for contaminants to "out gas" from the inner walls of the vacuum chamber, limit the scale of production. Currently, the technique is suitable for parts up to 20cm on the longest dimension. However, this is acceptable for low volume (one-off) production of high spec parts, such as combustion chamber and thruster nozzle units for communication satellites. Research is underway to scale the technique to larger dimensions or faster cycle rates.
If you'd like to geek out, you can read about it at http://www.google.com/search?hl=en&lr=&safe=off&q=ceramic+matrix+vps
Or if you're not a material science geek, check out _taraisawesome's boyfriend's band. Their initials are VPS but she didn't say what that stands for.
I also mentioned spinel mineral crystals, which are a class of minerals including ruby. http://www.google.com/search?hl=en&lr=&safe=off&rls=GGLD%2CGGLD%3A2003-33%2CGGLD%3Aen&q=spinel+armor&btnG=Search These minerals are the subject of a great deal of research for military applications, because they make excellent armor glass. The aluminum based spinels are especially promising for multi-hit survivability, and may be hot-press or sinter processed from powdered raw materials. If you need a windshield for a rocket car, this class of materials is a good candidate.