Small volume production, and a perceived cash-rich market.
Try eBay, try compromising where you can. I use a cheap fabric bag for my flight bag, a £6 stopwatch from Argos, keep my charts in a holder from Staples instead of something similar for many times the price from Transair...
A cardboard ASA whizz-wheel (or second hand RAF one) will work as well as a much more expensive Pooleys model, and a 50p WH Smiths Protractor will measure angles just as well too. Nothing to stop you marking a 1:500,000 scale on a bit of perspex...
You can save a lot of money if you need to.
G