HDMI licensing. The HDMI consortium charges the HDCP fee only on devices with a HDMI port so by placing the port on an accessory Nintendo does not have to pay a fee per device just per dock. Now you may point out that they are only offering bundles with a dock right now but this means if they do ever offer a dockless sku they don't have to cut a slice for the HDMI folks. If you buy a USB-C -> HDMI or DP -> HDMI adaptor the fee is included in the cost of the adaptor which is why a number of notebook manufacturers don't ship HDMI (also the port is too thick for ultraslim these days anyway).
These are the fees for HDMI 2.0:
http://www.hdmi.org/manufacturer/terms.aspx
$10 000 per year plus $0.04 per device if you adopt HDCP.
And these are the fees for HDCP 2.2:
https://www.digital-cp.com/sites/default/files/Notice_of_HDCP_2.x_Device_Key_Fee_Increase_0.pdf
$15 000 per year plus $0.01 per device.
They can't go around the $25 000 annual fees, at least because of the Wii U and first SKUs for the Switch.
You're saying Nintendo is building a plastic slab with some hardware inside that is costing them at least ~$10 to make, just so they can save $0.05 on each unit of a future SKU that doesn't exist yet but may exist in the future.
This doesn't make sense from a financial perspective...
The dock is snake oil to make the handheld look like a decent home console, which it is not.
I feel some people are not being fair.
It was pretty obvious from that start what Nintendo intends Switch to be.
Nintendo is trying to sell the Switch as a high performance handheld that you can dock for a good Home Console experience. It is neither.
What you're actually getting is a handheld with mediocre performance that you can dock for a Home Console experience that doesn't seem to be much better than 10 year-old consoles.
All this for $30 more than the price of a much more powerful
home console with the AAA game that won most awards in 2016.
Besides, what if you want your PS4 in another room? You're gonna disconnect it every time? No, you buy another PS4.
You buy a
$100 Atom+Windows box and you stream the games from the PS4.
This is assuming you don't have a windows laptop or tablet around.
EDIT: Forgot the Android app for streaming to Xperia phones had been reverse-engineered a while ago, so you can actually just spend ~$40 in a similar Android box and get the same experience.
The launch price is high, but it's probably artificially high in preparation for a Christmas price drop.
And what are they going to sell during the 8 months between April and the holiday season?