I am interested to know where Sarah gets this idea that the "electric bass as a cost-effective beginner's instrument" from.

What does cost effective mean ? Cheaper than an acoustic bass guitar ? Cheaper than a double bass ? Cheaper than a tea chest bass ?

Of course it depends on the quality of the instrument but I would not describe an resonable bass and amp setup as cheap.

What does a beginner's instrument mean ? Are Dave Pegg (Fairport), Ashley Huchings (Steeleye, Albion etc) et al beginners ?

To play the bass well requires restraint and musical sensitivity more than probably any other instrument.

Having said all of the above in defence of bass players I personally think that 9 times out of 10 just adding a bass player (guitar or double) to a traditional acoustic group doesn't work.

Ian