Sorry, this is not that 'crazy'.

You are talking about a difference of ~$50. The "crazy" fares on this before were hundreds more. If you want to feel better about it, starting next year, that G fare you saw will almost certainly be the going rate for BE, and not for a regular discount fare.

And the UA explanation is correct - they compete with low fare carriers on certain routes, and not on others. That is going to change the pricing - and always has. That's not going to change anytime soon - probably ever.