Why do we have to pay £150+ for the UK Jeppesen IAPs for the UK only, yet in California, which has many more airports, I pay about $25 ?
Because the FAA approach plates, as well as all the en route charts, are available free of charge for download
There are also several products for PDAs and tablet PCs which give you a Flitedeck-style moving map display, using this free data.
It's called a "monopoly"
Ably assisted by outfits like the UK CAA who could have done a huge service to UK pilots by releasing their charts free of charge in digital form, enabling the creation of moving map GPS products that display the actual CAA printed chart data, rather than the very sparse (and occassionally wrong - see the Class A airway depictions) Jeppesen data. But no, the CAA prefers to make money out of charts, so they license them out to Memory Map who in turn charge a packet for their PDA product. Which in turn is a dead end since no other European aviation charts are available, because the other European aviation authorities play the same game. So it's back to Jepp making a mint...
There is an open source project called Pocket-FMS but the whole concept isn't really suitable for O/S - the data updating is a continuous process which needs a commercial outfit to run it. But I do think that, for Europe only, one could put together a complete VFR/IFR map database for a fraction of what Jepp charge. Marketing is a big problem - Garmin wouldn't touch such a product...