It will be a fixed fee I imagine. The last horse to retire on a Private fee was Dubai Millennium in 2001 but those heady days are long gone.
I imagine we'll be looking at a figure on a par with Sea the Stars, €85,000. I'd honestly be surprised if it was over £100,000.
Juddmonte aren't known for doing deals with their stallions like other major stud farms, what they advertise they expect you to pay!