Thanks for taking the time to have a look and commenting.
You make a fair point, the cost is always an issue. It has to be a balancing act.
Each screen costs me a lot of money for the original artwork, and the license for the sounds (which can really rack up when you have so many objects involved). That, and the fact that coming up with original idea for scenes can be really difficult (there will only be eight scenes in total).
Also, I would have been happy to charge only 50p for two scenes but that was below Google's minimum cost allowed for all the countries.
I'm working in the hope that having screaming kids in the back of the car will inspire users to purchase additional scenes, just to get a little respite