I've opened 1k+ slayer boxes with 0 to my name. Bad RNG sure, but that still makes it rare. Not to mention slayer boxes are opened daily and i barely ever see an announcement of a crystal.
Donation store reduction still doesn't do it justice, it was 75 donation points for 1 before, now its 60 for 3. To buy 1 stone its 30t cash (thats assuming that donation tickets are even in stock at the store at all) to buy 3 its 90t cash and thats just for a single combat style.