It's interesting to look at India's Mangalyaan Mars probe, which cost $74M, or about a tenth of the NASA orbiter sent at the same launch window. This was largely because Mangalyaan was made out of completely standard parts; it was a tech demo for ISRO's satellite bus. (And it only carried 15kg of instruments.) It also only took 15 months to build.
So it's certainly _possible_ to build cheap spacecraft using mass production. You won't get anything specialised, so they're unlikely to work beyond the inner solar system, but you'll get cheap, simple and tested probes.
Whether this is _worthwhile_ is a very difficult question. Spacecraft cost money to run, and you're going to have to do very careful cost-benefit analysis as to what's the most efficient use of your money long-term. Plus, standard parts only work in standard environments; Jupiter's radiation belts would most likely kill Mangalyaan stone dead, even if had enough delta-V to get there, even if there was enough sunlight to run it.
But it's certainly worth considering designing a standardised long distance spacecraft bus, especially for missions to the outer solar system. Maybe someone's already done that...
(Mangalyaan is still in orbit, still collecting science data, still has years' worth of propellant, and AFAICT from the internets, has been an utterly textbook mission. They're sending another one at the next transfer window.)
So it's certainly _possible_ to build cheap spacecraft using mass production. You won't get anything specialised, so they're unlikely to work beyond the inner solar system, but you'll get cheap, simple and tested probes.
Whether this is _worthwhile_ is a very difficult question. Spacecraft cost money to run, and you're going to have to do very careful cost-benefit analysis as to what's the most efficient use of your money long-term. Plus, standard parts only work in standard environments; Jupiter's radiation belts would most likely kill Mangalyaan stone dead, even if had enough delta-V to get there, even if there was enough sunlight to run it.
But it's certainly worth considering designing a standardised long distance spacecraft bus, especially for missions to the outer solar system. Maybe someone's already done that...
(Mangalyaan is still in orbit, still collecting science data, still has years' worth of propellant, and AFAICT from the internets, has been an utterly textbook mission. They're sending another one at the next transfer window.)