And they can be cheap. Like, really, really cheap.
While one could get uppity about how much of a waste of money the carbon fibre delight linked at the top is for anyone other than a professional road rider, or snobbish about the 'bike shaped object' illustrated from Cambridge market, I think both exclamations miss the point.
Cycling can cost you, basically, more or less whatever you want to pay in its initial outlay. And then for just a few notes you can keep riding - the occasional repair or, if you paid a tenner, some free time and the willingness to scavenge more parts, will get you where you're going. It can be very expensive or it can be free.
The weird idea that cycling is for posh people, rich people, paupers, young people, men, women... Its all complete crap. Cycling is for everyone - if you've a tenner or a million quid, its for you. Its the great leveller - get a bike, any bike, and ride it. And thats all you've got to do.