That’s sort of my original question - is it just marketing BS why these bikes are nearly 5 figures or is there some magic to them. Bit of both I’d imagine.
I’d expect to be bombarded with marketing bs / science (pseudo or not) if I was shelling out that sort of cash.
I think you are correct in saying it's a bit of both. I retired four years ago and from my lump sum treated myself to a summer bike which would now cost £4500, possibly £5000 given the price increases coming our way, to replace. I didn't pay close to that sum. The difference is significant, my easy cruising speed increased by 3 mph and it has been a contributor, not the only factor, in a huge improvement in my hill climbing.
Another aspect is adaptability and uses. I recently bought a winter bike for £3000+. Sounds outrageous for a winter bike. It would be except we chose a frame and set up which gives me a winter/gravel/touring bike and would also make a decent summer bike. So 3-4 bikes in one.
Paying £5-10k for a bike would be very hard for me and I doubt I'll ever need to. The reason is this. I think, for example, 105 is very adequate for my needs. I've watched too many friends struggle with Di2 so I want traditional shifting. Therefore I'm unlikely to invest huge sums in Ultegra and Di2 as I see no benefit to MY cycling.
Show me a frame and wheels which will improve my riding and pleasure and I'm sold on it.
I recently spent £500 on a secondhand Cannondale. Why? It will fit perfectly the use I have in mind, it's a beautiful bike and I've always lusted after a Cannondale. It isn't about price, it's about purpose, benefit and pleasure in equal quantity.