Nintendo Switch Dock Set - $72.99 plus tax @ Target and Amazon
Cheapest I have seen this official offering go beyond various YMMV clearance deals (retail price is $89.99). Still rather expensive, but a good discount for those that want another dock but would prefer OEM to avoid potential complications from alternative third party offerings (some have experienced charging and display issues, etc). This set from Nintendo does come with a power adapter and HDMI cable as well.
Could save even more with red card or other usable promo codes.