> 15 years ago middle of the road mountain bike could be bought for around 200 euros

You couldn't ever buy a 'middle of the road' MTB, or any kind of bike, for €200. You could buy a piece of junk that falls apart in 2 years for that kind of money. A decent commuter bike starts at around €750.

> Bicycle tires cost about the same as my car tires.

Where do you get new car tires for ~€20 ?

> This is turning into a rich-man hobby.

Over here (the Netherlands) cycling is just a mode of transportation for most people. and it's by far the most affordable one there is.