USB-C is way more complicated, even if you're not trying to push 4K video or 100W power through it. The interface chip ought to be more complex, and thus likely more expensive.
You can still find a number of cheap gadgets with micro-USB on Aliexpress. Likely there's some demand, so yes, you can build a consumer product directly on the dev board, depending on your customer base.
Yes, indeed, I've checked, and apparently you don't need anything beyond this if you don't want super speed or power delivery (past 5V 3A).
I did not realize how many pins in a USB-C socket are duplicated to make this possible. (For advanced features, you apparently still need to consider the orientation of the inserted cable.)
You can still find a number of cheap gadgets with micro-USB on Aliexpress. Likely there's some demand, so yes, you can build a consumer product directly on the dev board, depending on your customer base.