Yeah, there are a few crazy NZ collectors who seem to think the old Jansens are solid gold or something.
I've never laid my hands on one, but on appearances they don't seem like much of a step up beyond the eastern european offset knock offs.
The amps though, go for a couple hundred all day on trademe.co.nz. Great cheap old tube amps (despite the name they're not actually bassman clones). See also Holden, which were basically Marshall clones, the founder of that company moved to Aus and started Wasp amps. Which were used on the first few AC/DC records.