On the other hand, look at the contents of a pilot case of an *experienced* pilot, and compare it to the catalog of your average pilot shop. There's a huge discrepancy between what you really need, and what the novice pilot thinks he needs. I think that's what the market for pilot shops is really about: Student pilots that have too much money on their hands but not enough opportunity to spend it on flying (after all, the next lesson is only next week...)
The timepiece that seems to have become the subject of this thread is a case in point. Yes, I have fallen victim to greed and bought the ASA flight timer. Never used it in anger once. Always used my analog watch, until yesterday, when I forgot it. But the on-board GPS displays UTC as well, so I simply used that. (Obviously for IFR hold timings you need some sort of stopwatch but any sub-10 UKP stopwatch will do.)
And there's other stuff. A few days ago I bought another pack of 100 A6-sized "correspondence cards" for 1.79 euros. Like a postcard, but completely blank. Those are going to be my plogs for the upcoming few years. Or my aerobatics sequence cards. Or my flight record cards to keep track of block times and tacho readings. Or as instrument cover when something is U/S. Together with a lead pencil, which is also used to mark up the map, it's all I need. Why would pilot shops need to sell 4-packs of pens in different colors, with the proper eraser, and kneeboard clips so that you can attach three different color pens to your kneeboard? Or four different types of pre-printed plogs?
Sick bags? A pack of zip-lock freezer bags from the nearest supermarket.
Flying clothes? My wardrobe already contained everything I needed.
Sunglasses? The ones I keep in the car do just fine.
Approach plates and such? As mentioned earlier, the AIP contains all you need, and is free. (Use the Eurocontrol site to get the AIP of all of Europe.)
Aviation GPS? My Garmin eTrex Euro plus OziExplorer, bought well before I started flying, served me well over the years. My 3G iPad now does the same thing for the price of just one App (Air Nav Pro). But frankly, on the majority of my flights I don't even bother with the GPS. Visual navigation/dead reckoning is really not that hard in VMC. (And for IFR flying with RNAV capability/routes, you need a certified panel-mounted GPS in any case, not a handheld one.)
Kneeboard? I bought an aviation one but frankly any A5 sized clipboard would do. Or A4 or A6 if you prefer. Available in any office supply shop.
High-viz vest? From the nearest DIY shop. In fact, I got mine for free at some event I attended years ago.
Checklists? The (authorized) club checklists for all our types of aircraft are available as a PDF download from the clubs website, so you can print them yourself. Or you can buy the laminated ones at the club, for 2 euro each.
That leaves the headset, fuel tester, E6B flight computer, logbook and the aeronautical maps as the only things in my flight bag that are proper aviation things, and have no substitute in the non-flying world. Is that honestly what we're concerned about? The pilot shops making a profit on a headset or fuel tester?