Is that $10 each or are there bundles?
That would be roughly $10 for each, so "Symphony Woodwinds", "Symphony Strings" or "Berlin Woodwinds" would each be separate libraries.
To make this clear, the MuseScore libraries
only work with MuseScore.
If you're not interested in using MuseScore, or are happy with the free MuseScore sounds, there's no reason to look at this. For a BiaB user, using MuseScore means using a different tool to notate, render, and integrate those sounds with BiaB tracks. That's already a fairly small subset of BiaB users.
MuseScore already comes with MuseSounds, which will give you a full set of orchestral instruments - both full string sections and orchestral soloists, as well as guitars and other instruments. So
none of these additional instruments are necessary to use MuseScore.
The advantage of using MuseScore instruments with MuseScore is that they are tied to the program's notation, so they work automatically with
pp,
pizz, turns, and so on. Currently, commercial libraries can be used, but they are not yet integrated with the performance notation. So you can use Miroslav Philharmonic 2 in MuseScore, but you've have to jump through hoops to get the strings to change from legato to staccato.
But rumor has it that support for popular commercial libraries will come eventually.
All of the libraries I mentioned are available from the vendors are full, stand-alone libraries. For example, Spitfire sells their
Chamber Strings library for $374. It consists of Violins 1, Violins 2, Violas, Celli, Basses and Ensembles and supports a wide variety of articulations.
The MuseScore version of Spitfire Chamber Strings is derived from that library, but contains a cut-down version with only a single microphone position, and less depth of sampling. Again, it only works with the MuseScore library.
What these libraries give you is the "sound" of these commercial libraries. If you love the sound of the Berlin orchestra instruments, the MuseScore version of the library gives you an affordable way to get a reduced version of that sound that's integrated into MuseScore's notation.
I hope this clarified the initial post.