Cheap Resource or Overpriced Toy?

I once boasted, somewhat immodestly, that given a class and a ream of A4 paper, scissors and glue, I could run an event for a whole day... To my extreme happiness, nobody has yet asked me to prove this, but I think the principal is still sound, it is the teacher that is the best resource, adapting the resources to their need. This has been proved in reverse many times and evidenced by the store cupboards of robots and techno gear in most schools, bought for some wonderful project, often based on the skills of a particular teacher, then when it or the teacher proves unable to fulfill their promise, the resources are quietly squirrelled away. Too valuable to dump, too complicated to use, and eventually too old fashioned to be applicable, such resources wonderful convoluted surfaces prove excellent at gathering dust, and for a few teachers, guilt. Many science departments suffer the same ignominy with beautiful glass cased mahogany framed instruments which are wheeled out once a year to demonstrate Boyles law and refresh the happy memories of the senior departmental members.
I got bit by this bug about 8 years ago. RealRobots was one of those magazines where you collect a piece an issue to make the robot. It was actually very good, and at a time when robots were very expensive, it promised, in 40 parts, a real programmable robot with advanced features. Unfortunately about issue 30 it became clear, despite my careful research before I convinced the Deputy head to buy a THREE subscriptions, that everything was not quite rosy and we would have to extend the subscription a further 20 issues per robot (Total 60) to get the controller... and pay extra to get features that were trumpeted as standard at the start. I pulled the plug and had to admit to the Deputy Head that I had been wrong, worse the school had lost a few hundred pounds. RealRobots, it turned out, hadn't got a complete product when the series started and there was a great outcry from buyers wanting to know where their promised 40 part controllable robot had gone.
So resources are a minefield. You can keep a class of toddlers happy with a few trays and a packet of cornflour for hours, you can also use the same resources with a Technology class to talk about materials science, thixotropic materials, bullet proof vests, Sorbothane and 'D3' energy absorbing phone cases. It is the skill of the teacher that matters, and their research before the teaching session.
So a real puzzle was the low sales of my PopGlider corrugated card plane through www.ajbox.co.uk . Developing the plane as a set of resources, including 3 presentations, teachers guide, worksheets and demonstration films, I expected it to be taken up by many and used, as intended, as the focus for practical learning around Materials Science, Flight, Air Density, Quality of Construction and many other areas. It seems though that it gets used as a filler, something to quickly build and try out with a class, and therefore, at £1 a plane, relatively expensive. I thought that all those free resources would encourage people to use the PopGlider to its full potential, without the resources it is a dull sheet of card, however brilliant as a plane... Of course, being made out of 100% recycled card and 100% recyclable, I could always eat them!