British Airways American Airlines Hidden seat assignment surcharge for codeshare from American Airlines

If you book on American Airlines for a codeshare on British Airways, in business class, neither AA or BA discloses until you have paid in full that you can only get a seat assignment in advance by paying a large per-segment additional charge.  American does not charge it for its own flights but British does and does not tell you in advance or how much.

There is nothing on their website to warn you in advance about it or how much it will be.  Using their chatbot web service gives no information and is useless.  Calling their 800 number results in a recorded message saying that they are very busy and one should call some other time.  Repeated calls yield nothing.

This is an example of bait-and-steal, and BA has been doing this for years.  Iberia through codeshare does the same thing.  Being part of OneWorld means nothing.

You buy and pay and pay and pay.  No idea when it ends for them.