CAA own the aeronautical data, which is freely available. They do not own the base map, which, as others have pointed out, is owned by Ordnance Survey.
Given the reduction in detail on the half mil base map one would expect OS to charge less.
An idea of the value placed on the data can be drawn from
this press release. In 2001 the AA agreed to pay Ordnance Survey 20 million pounds to settle a dispute over copyright.
Another tack would have been for the CAA to make their own charts, not using O/S data. That would have been much smarter, and for that little backwater called UK would have been pretty easy.
You don't half talk rubbish sometimes. It takes a small army of surveyors to map something the size of the UK and to keep the data updated. OS recovers that investment by sales of a humungous range of products (which go far beyond maps) both within the UK and overseas, which bring in a revenue of over 100 million pounds pa. If it's "pretty easy" to map the UK and recover the cost from VFR chart sales then I'm Saint Francis of Assisi. For Comparison the entire CAA Group turnover in 2006 was 173.4 million.