Well i know a LFS that sells LR for 5$ a pound ( canadian $ ) and it is a rip-off 'cause their live rock sucks..it's like 90 % base rock bathing with cheap live rock.
If the LR in your store looks good no it's not a rip-off
around here at my lfs, the good figi/tonga lr is 7.99 a pound, and they have some marshall island live rock for 12.99 a pound, 5 sounds good as long as its good quality (as mentioned ealier)