Its all diminishing returns, isn't it?
Lets face it, with 60-odd years of manufacturing know-how, in 2015 its almost impossible to buy a really bad bass guitar anymore. Certainly, once you get over £300 (£200?) almost everything will be decently made, sound good, stay in tune, and be completely giggable. Bass guitars that cost ten times that price will (or should) be exceedingly well made, sound great, stay in tune, and be completely giggable. The difference is In the details---the aesthetic, the feel, the nuance of the sound, etc.
For me, I've never found a bass that would justify spending more than £1k on it. Its a personal decision. Do the differences in the details matter to you more than the price differential?