A dutch women told me once a story, where she but a used bike in Amsterdam and the heroin addict who sold it to her, threaten her to steal it again, if she does not use a heavy lock.
When I moved to the Netherlands my boss told me to never spend more than 20 euro on a bike because it will get stolen. I didn't listen, and lo and behold two weeks in my 75 euro bike and the 35 euro heavy duty lock disappeared
I've never done it, but you buy it from the thief (junkie) directly. So it could be that you find them by word of mouth, like you would use to buy drugs when they were illegal. But you can also buy a second hand bike very cheaply, some are even free (just an example: https://www.marktplaats.nl/v/fietsen-en-brommers/fietsen-her...). New bikes are usually more than 200 euros, dutch brands are 500 euros and up
It seems like that that point the bike thieves are just a bike rental company.
You get the bike for < 20 Euro and then, presumably, at some point in the future it gets stolen again, but you already got 20 Euros worth of use out of it.
This was 2010-ish and I found one on Marktplaats. Might be going for 40 or 50 now with inflation. People selling them on the street also had for cheap, but these were most definitely stolen.
The Netherlands famously has more bicycle thefts per year than citizens. At this point you could almost think of cheap commuter bikes as public property.
People in countries where bicycling is not seen as a personality statement generally ride very cheap city bikes around town. Last time I bought one of those in college it cost about 30eur. Is not like in SF where people ride 3000 dollar bikes to work because omg you’re a cyclist now and this is your whole identity.
Here in the part of Canada I live in, you see some of the $3000 bike identity stuff, but most people ride something in the $500–$750 range. Something practical, comfortable, reliable, etc.
There is also a growing segment of people who use $5,000–$15,000 cargo/kid carrier bikes as replacements for their cars, which is cool. But I do worry about theft of those increasing. Right now I rarely hear of it, but it seems likely to increase. Even the motors and batteries in them cost thousands alone.