Mask ROM is actually pretty expensive to manufacture, which is why original DS game carts were so small you could fit a hundred of them onto a $20 MicroSD card

Mask ROM is actually pretty expensive to manufacture, which is why original DS game carts were so small you could fit a hundred of them onto a $20 MicroSD card during the same time period. The upside of course is that your original DS cartridge might never go bad, even if you lose it under the sofa for 30 years. This is not true of modern switch cartridges.