What sound is that? I have played 6 60s jazzes and they haven't sounded the same. In fact, from sound I wouldn't be able to put a decade on anything. The best sounding Jazz I ever played was a 1965 jazz, sounded great (no use though, not enough strings). However, one of the worst jazzes I have ever played was a 1966 jazz - a squier affinity would have probably sounded bettter, anything would. The 66 was more expensive though as it was original, whereas the 65 had had a refret and had a replacement pot. And frankly what they sound like or play like is not really so important to their value.
There is no bubble, it is an appreciating asset, there are (and can be) only certain amounts of 60s basses, that number is going down, and the number of people with disposable income is going up, so they will keep appreciating. There are no shortage of bankers or stock brokers who have a display case for one.