Do you support the online sale of lesson plans?

This is a tough question to answer. I love sites that share lesson plans because I get ideas from them and then tweak the lesson to fit my style. I would not pay for being able to do this. On the other hand, when there was no textbook for my technology class, I developed all the lessons for my students. It, as you can imagine, was a tremendous amount of work that I did at home and at school. Most of my work never left my classroom although if a colleague spoke of needing a way to teach some content I would share a lesson with them. Because of my hard work when I retired I took all of the lessons with me. My rationale - the next teacher should plan to work as hard as I did to provide students with what they needed. I don't think I would have marketed my lesson plans for other teachers especially since teachers spend enough out of pocket already.

many education systems attempt to portray the creation of work during hours as 'owned' by the institution.
Not so.
English/US and Australian law recognises author right, so the IP can be sold to the highest bidder...

whether some of these plans are worth the monmey..and who buys them is a completely different issue.
perhaps the publishers will need to share a greater proportion with the creators of the work...currently 10~20% (30% if established!) Something like iTunes for teachers would be a better option

I believe lesson plans are personal work and teachers should profit from their creative work if they so desire. However, if the plans were developed during school hours, the profit should be used in the school or classroom. There probably isn't any way of monitoring this, but it is the ethical thing to do. Selling lesson plans does not prevent the flow of ideas between teachers if they choose to do so.