Originally Posted by
dmp1991
... They even get to set the price! So I'm effectively paying with cash at the rate they set. ...
IMO, it's just silly for the airline not to offer you the opportunity to buy any empty seat whether paying cash or "points" or Avios.
If there are empty seats, you always have the chance to buy any empty seat with cash. You simply ask to change your ticket for the change fee and fare difference.
The real problem with BA's model for you is that you don't like the price they've set.