As of now, Be'lakor, the Dark Master, Magus Lucea Kane, and Marneus Calgar all rank around the #60 #70 most popular commanders in genera according to EDHRec
1 Blood Pact
(Plus, it's only a one-of, so cutting it wouldn't really reduce the deck's cost meaningfully anyway.) The one rare that can be cut is Castle Locthwain, which, as we discussed, is very good and, outside of costing some wildcards, is mostly a free-roll in the deck but not all that important
Nearly all of these cards are relevant and desirable for Constructed formats, and some are also worth serious money (for rares, that is)
The prolific price rise, and particularly the recent spike, may well have something to do with the upcoming The Hobbit set, releasing in August (check the MTG release schedule here)