Nice rock!
I picked up around 40# from my local retailer for $4.50 a lb. The remaining 130lb I picked up from a local fella I found on craigslist who was tearing their tank down for $3 a lb, the larger pieces (one piece alone is 40lb) for $2 a lb. The benefit of this is they didn't need to be cycled, and already came with tonnes of coraline algae, soft corals, and all kinds of good critters crawling around.
On the topic of macro algae, is there a link that explains what all the different types of macro are?