What do you mean? Nintendo decides what options are available for their console and how much they cost.

They could have made both card options cost the same. They could have more than just a 64GB option at different costs for larger or smaller games. They could have made it a requirement that the key carts are only able to be used if the game doesn’t fit on the options with storage.

There’s a lot of other options than just making the objectively inferior option significantly cheaper.