Maybe outside of the denser urban areas it's cheap. Inside them though, I can't imagine how one could justify it being "cheap". Everything is built up already with cars in mind. You might say "Turn an existing car lane into a bike lane" - that is vastly more complicated than you might think. You're reworking traffic patterns, displacing parking spaces, and in the end just painting lines on the ground that no driver is obligated to respect. In some cities that can be an utter nightmare - I'm thinking mainly of DC here with the convoluted road network(which already has a few bike lanes and more on the way, as well as a widespread bike-sharing program). I want bike lanes or otherwise improved bike access too, but it is an immense proposition for a dense urban core that was developed around the automobile. In a lot of cases the issue is not that there is a lack of demand from the people or attention from public officials, it's that the planning and execution involved can be a nightmare.
I dunno why people downvote what they "dont like to hear". Sounds pretty much accurate to me (some guy is going to tell me my opinion doesnt matter if its not baked by graphs tho).
In SF, there are quite a few bicycle lanes. That's cool. Half of them are ruined by parking. That's not cool. Half of my bike-riding coworkers have been "doored" so far.
Heck, it's still a lot better than no bike lane, but it's hard to get right since the space is already taken by car lanes and parking lanes.
In Paris, even thus, as per previous posts, scooters ride on it, some lanes are actually part of the sidewalk and are forbidden to pedestrians.
In Germany I've seen that too (albeit theyre not as well designated IMO). Advantage: no one car park on it. No car can even cross them. Feels a lot safer.
Unfortunately in Paris that's not the norm, its only a few places where they were able to do that.
