I love RBVs but they are not a $1500+ used bass.
The market will dictate this, not our opinions. I've seen RBVs go over $1500 in completed listings several times, though I tend to agree with $1400-1500 as a median or mean value. Mine sold for $1400, but I never went to eBay with it where it might have captured a much wider audience.
I also follow Ric basses. You should see how the value of the 3001 and 3000 basses have shot up... For years they were regarded as an afterthought. And now the 2000 series basses are doing the same. I'm sure many 5-10 year owners are seeing double to even triple investment value on basses like these.
RBVs, as a discontinued model, fall in the same category. Demand will probably always exceed supply, at least for the next 50-100 years (after that maybe no one cares about them anymore except a small few). While this is still true the prices will keep on going up.