It's the boards that are for development, not the chips. They are intended for development of a product which includes the chips on them, not as general purpose

It's the boards that are for development, not the chips. They are intended for development of a product which includes the chips on them, not as general purpose glue like raspberry pis or arduinos. And for this kind of development the cost of the boards is usually negligable compared to the other costs of development, so there's little price pressure on them (especially compared to competition on the price of the chip at scale). In fact it's generally in the interests of the companies producing such boards that their limited supply does not go towards people not intending on buying at least few thousand of their chips (and if you give them an indication that you are likely to buy a decent quantity, often you will be given these boards for free). That said, there are sometimes modules like those mentioned in the article which are intended for production use in volume, though generally these are aimed at a segment of the market where there's about the right volume that saving the development costs of putting the chip onto the custom board direct (e.g. the PCB layout connecting the SoC to the DDR memory or getting a prototype board with enough layers to bring out all the signals on the chip) is worth the extra markup.