But this is upfront, during training?

How does X then change "on the fly" if ad deals are changing? Constantly re-training with whatever advertiser is the current highest paying on?

In google ad times, this was realtime bidding in the background - for AI ads this does not work, if Im right?

Companies pay for entire sports stadiums for brand recognition. That’s also not something you can change on the fly, it’s a huge upfront cost and takes a significant effort to change. That doesn’t stop it from happening it’s just a different ad model.