Unless housing materials use things that aren't already flooding the market due to their nature of being simple gathered materials, that's useless. He said maps won't be reliable for tomes, so that's useless. I may have missed it, but I didn't see him mention tome materials, but again, it's probably still faster to spam WP. Rank III materia, oh thank god; I couldn't get those already by spiritbonding crafted gear or anything like that.
Beyond the initial runs to experiment with the system, I have a feeling that people will only care about maps for the "5-6 rare pieces you can obtain." One (or more!) of which will no doubt be a minion.