Bikes are a bit like cars, once you've spent a certain amount there are very, very few really crap ones.
As to brands/marketing, people will pay far in excess of a products costs if they believe the hype - you've only got to look at the high 'value' fashion items. Many years ago I did some work at an importer of materials and silks - they were buying scarves in at dozen for a pound - that eventually ended up in Liberty at £50+ each.
As for bikes, for me the cost of the frame is irrelevent - its how it rides thats the key. But its in the components where you can make a real difference, and usually money talks.
Its also very enjoyable in buying a mainstream bike, and then swapping and buying top end stuff over time - whenever deals and/or breakages happen.