When I bought my rock for my tank (225 lbs) I got it from
www.Marcorocks.com and it turned out to be pretty darn good rock. It was dry rock though I'm not sure if your client is willing to wait to cure it and get good
coraline algae growth. But, I have pics of what my rock looked like when I first put it into the tank (BRIGHT WHITE) and now 7 months later huge amts of
coraline algae (between 30%-60% coverage on the vast majority of the rocks). And all I personally seeded the tank with was about 30 lbs of fully established LR from my other tank (*2* 15 lb rocks). When I purchased the rock I bought it off an ebay auction and only paid $1.65/lb Shipped Price. So, it's very reasonable and you have the option to buy massive show pieces (some of his show pieces are over 100 lbs each).
Jason