Was that a 4x10 or a 2x12 bassman? In any case, these represent used prices in 1968.
For what it's worth, I seem to recall a new Jazz costing $260 in 1965. I might be mistaken, but the P-bass was about $40 less in my memory. I can't seem to find an old price list on line. Anyone have one?
Assuming a 1965 Jazz WAS $260 in 1965, that's $1,739.90 in 2008 $ according to Tom's Calculator. Instruments were not cheap then.
Don't get me started on investment. For some reason people think that if they have a bass that appreciates, that makes it a "good investment." That is not an investment IMHO, good or bad. It is simply the appreciation of a single rather limited asset.
IMHO, an investment is something with the right mix of reward and risk that will allow you to reap very significant returns, like, oh say half your annual income or more---for life. This kind of investment generally requires many years and a lot of discipline. Darn!
examples: a small business, an education, retiring with $100k/year at age 60, etc.