Composer: From free (for the experience and credit) to a few thousand
(for a new composer with experience) to five figures (for a name composer).
Musicians: In my experience it's really hard to find good string players
for free. I once used a college string ensemble. While they were all enthusiastic
it took several days of rehearsals and several studio days to get the score
recorded. An expense I wouldn't repeat.
Experienced musicians are expensive and well worth it. I have never hired
an orchestra. My assumption is most of the best ones are union and would
be very expensive. I have only recorded a section at a time - strings for one
or two days, brass, winds and percussion on different days. That might not
work if a full orchestral score is needed, but for a nice sound it is amazing.
And I know the synthesized sounds are getting really good - but I just prefer
the feel and texture of recording live players. On my noir thriller I used a
six piece Jazz ensemble. They had a written score, but riffed off of the video
playback of a few of the scenes and that really added a great feel to the scene.
My total cost for a feature was $15,000 - including mixing.