In Europe taxes are a lot different so things often cost a lot more (like that jeans example). Some 15 years ago you could get a good bike for 300 punds, but today, looking at that price range... naaah. Cheap parts, often poor quality.
@OP: the black marks on wheels are normal brake pad wear+road dirt. That's why I prefer black tyres... and pants.
I admire that you're riding a bike without fenders in the UK!