Well, of course they cost a lot more, so less people can afford them, and therefore less are made. Also, one is less likely to part with one for reasons of upgrading to something better, as there isn't anything better -at least, not electronically nor qualitywise. The only reason for wanting to part with a series II would be some other reason, like wanting/needing ebony laminates, or having a lighter instument and/or one with different balance characterists, woods, or some other thing.
Furthermore, I suspect that if one were to investigate, one would find that most series II owners have owned other basses, including other Alembics, and have, by the time they've commissioned their series II, a REALLY good idea of what they want. Common sense/logic might suggest that as a group series II owners are perhaps at least a little bit more likely (given my assumptions of previous ownership/experience of/with other basses) to know exactly what they want and are therefore correspondingly less likely to part with what is probably/hopefully the ultimate/perfect instrument for them.
More likely, they might order another that represents a different paradigm of some sort.
