Is there data that market rate has zero margin left when it comes to renting? Genuinely interested. Where I live, I have received direct reports that there is

Is there data that market rate has zero margin left when it comes to renting? Genuinely interested. Where I live, I have received direct reports that there is almost zero margin between building cost and market price (buying). But buying and then renting still has a good ROI, although a longer term one. I don’t get it, it goes against the market self regulation, but real estate is very twisted in this respect.