I only got to glance at them, but I could tell that I liked them. My players get to scope a dragon's horde tomorrow night. This, as well as stuff from some of the other recent excerpts, will definitely be showing up.
I don't see cost as that much of an issue. More than just gold cost, there's the action cost. It's a standard action to plant it. It's probable that some other actions would benefit the players more. I think that it will help the planning stages of things. Knowing where to plant it before a combat would also help make things interesting. I look forward to seeing more of these.