I am a teacher, and I looked at those lesson plans the last time this was in the news. Most of the lesson plans were crap--I fear for a world in which many teachers pay money for crap like that because they aren't even able to make crap like that on their own.
The main reason I can neither be a customer nor a seller in a marketplace for teachers' lesson plans is that I use rarely used (that is, actually good) curricular materials for teaching mathematics at the "prealgebra" level,[1] and few other teachers use those. Most other teachers who do use the same materials I use are both smart enough to specify using those materials and smart enough to write their own lesson plans individualized for the classes they teach day by day.
The main reason I can neither be a customer nor a seller in a marketplace for teachers' lesson plans is that I use rarely used (that is, actually good) curricular materials for teaching mathematics at the "prealgebra" level,[1] and few other teachers use those. Most other teachers who do use the same materials I use are both smart enough to specify using those materials and smart enough to write their own lesson plans individualized for the classes they teach day by day.
[1] http://www.artofproblemsolving.com/store/item/prealgebra
http://www.amazon.com/Math-Focus-Singapore-Teachers-Edition/...