''Yaughting and horses come to mind.'''
Yachting can be expensive, but not in every area. Sailing electronics are much cheaper. For example, the VHF radio I installed in my boat last year has many more features. It's got variable transmit power, digital SELCAL, a meesaging system, the ability to automaticly transmit a distress meaasge including position, and listen to three frequencies at once. It can also link to other electronic systems to transfer data - and it's waterproof. It cost about 160 GBP,whereas the less capable aviation equivalent will cost five times more.
Of course, it doesn't have to be certified and I expect the production run will be greater, but the price disparity is just too much to explain. Could it be that pilots are being ripped off?