Let's leave aside the polarised positions that various debates about this situation have created - she's a money-grubbing chancer / he's a privileged idiot, and ever permutation in between.
And lets consider the reasons why this settlement has been reached.
Allowing for the fact that we have absolutely no idea of the evidence that may or not be forthcoming from either side, my assessment of the situation is this.
Ms Giuffre's lawyers may have said to her - You can have your highly desired day in court, and expose Prince Andrew as a liar and an abuser, and hopefully win, no guarantees, and be awarded twelve million pounds. His side will then appeal, and you may see the settlement in twenty years time when they have run out of excuses not to pay.
Or, you can avoid the horrible trauma of a court case, see him humiliated and tainted for ever, and get twelve million pounds within thirty days, guarenteed.
Which would you go for?
And from the prince's side -
You have dodged, and avoided, and looked utterly shifty and immoral throughout this process. You have added to that by blatant victim shaming and a refusal to acknowledge the abuses carried out by your friends. If this goes to trial, her lawyers will eat you for breakfast and your family will be marked for ever by the scandal. If she wins, and its extremely likely that she will based on the evidence, she may be awarded hundreds of millions by the court. Or you can pay twelve million now, and the court case stops. Which would you go for?
That is a possible example of how they arrived at the settlement.