Well I looked but I couldn't find Waterson Carthy anywhere or anything cheaper than £6.

I did notice that some folk CD's on offer (Anne Briggs for example) were remastered tracks from vinyl LP's that are no longer generally available.
In such cases they are encouraging people to become familiar with artists who stopped recording many years ago.
The Norma Waterson CD for example has a terrific track of Aint No Man Worth The Salt Of My Tears not previously released.

I really fail to see how the release of such material damages the artists. The Topic Samplers of the past did a similar thing very effectively.