COMC has been pretty diplomatic about this whole issue but just going through some possible rationale behind this whole movement. Some purely speculative reasons could include
1. Beckett just wants too much money for using their data.
2. Beckett's data is not comprehensive enough to cover many sets that are not listed there.
3. Beckett's book value is completely crap and out of touch with the actual sale value.
Again, these are just pure speculation but what other possible reasons can there be?