The only reason I want them is that they give a nice uniform look to my mostly GW army. Mantic ones will look out of place somewhat. I am not hell bent on them but I quite like the models. I suppose the Mournful Knight models are much nicer and ideally I'd rather have those, however I heard they are a pain to assemble plus they won't fit in with my army look again :/ But yes I agree the full price for Blood Knights is ridiculous.
What I find funny is that instead of lowering Blood Knight prices to match the prices of the rest of their range instead they are raising the prices of everything else so it is like the blood knights