Lenovo sells many laptops which cost much less than Thinkpads. Thinkpads tend to be the more expensive models. A quick search for "macbook" and "thinkpad" prices between $900 and $1300 for macbook and between $400 and $999 for thinkpad. Searching for a regular "Lenovo laptop" (excluding Thinkpads) I see prices as low as $190.
Not necessarily true -- maybe for the X1. However you can get a similarly specced T450s for less than a 13" MBP.
I just bought a new laptop and did comparisons between Dell, Lenovo, and MBP. I ended up with a Lenovo T450s (one SSD running Windows 8.1 and another m.2 SSD running Ubuntu).