Here in the U.K. I'd say that maybe 1 Cup comes up for sale per year, currently at a value of maybe £40k approx (depending on mileage/condition). Also, maybe 1 manual Ghibli GT will come up, at a value of around £15k approx.
You could easily have to pay over £20k for a top quality, late, low mileage RHD manual Ghbili GT. But at the same time, an earlier example in lesser condition could be had for less than £10k.
The problem you will have is that so little comes up. Hence looking in Europe for an LHD car is a far more simple option. Indeed, my first Ghibli was a 2.0 lt (306 bhp) LHD car from Italy that I sourced from David Askew.