A recent post started a brief conversation about the disposable nature of the bikes most people are riding in Tokyo. These "mamachari" and kids equivalents, cost only 10-20,000 yen, so if they get old or rusty, much easier to replace them than to repair or maintain them.
Today, as I passed through Tachikawa, I went by a Cycle Base Asahi store just as a truck was loading up junky traded-in bicycles. I asked the driver ... dragging bike carcasses out from behind the shop, how many weeks worth of bikes is this? Answer: One week. Typically 50 bikes a week disposed of, at this one shop.