Originally Posted by
SamOF
...or the huge number of people who purchase a non-refundable domestic flight for less than $200.

The cancellation fee is still $200, regardless of the cost of the ticket. There's nothing that says this fee needs to only come from the base fare part of the ticket.
So if you bought a ticket that was $150 plus $40 in taxes, UA is going to keep the $150, start to hand you the $40 in taxes, and then say 'but wait, you still owe us $50' and keep it.
Technically they could probably then say 'and you still owe us another $10' but obviously that's never going to actually happen...