I just looked at their web-page... if their "normal" price for a "46-52lb box" is $520, thats an average of about $10 per pound... that's REALLY HIGH. even their super special ultra low price for only the next 24 hours (yea right) isn't that great. it'll average out to about $2.50 a pound but you'll still have to pay shipping on that. If you look at liverocks.com as a comparison, their 40# box is $200 and INCLUDES shipping. That breaks down to $5 a pound but dont forget, that already includes shipping.
Just remember... if something sounds too good to be true, it probably isn't true.
And i'll second lando's comments on PC
. its a very affordable middle ground from NO
. I noticed a huge difference in my tank going from NO