A few years ago now, I saw a craigslist ad for free bricks. A mason was working on a renovation of a century+ building that involved cutting new windows into the old brick bearing walls, and couldn't bear the waste of good brick. He said there were dumpsters full of brick that went to the landfill before he placed the ad. He would have taken them except that he couldn't store them. I picked through the dumpster at night (in a back alley behind the building), and filled my van with a full load of a couple hundred bricks several times, and ended up with probably enough bricks for the non-core parts of two RMHs each for me and my best friend.
Another craigslist ad netted two overfull van loads of firebrick, unused but slightly dirty and mossy, for about $1.25 each. You can see some of the spoils in my
RMH build thread.