I have 2 friends who have had GT's.
Both have more than enough money to run them but in the end its the costs of running them that have pushed them both to sell them..One of them was a 57 plate,and was sent in for a service in Wilmslow,brakes inc 1 caliper and some other remedial work needed to be done,bill was a shade over £7000 if he wanted to go ahead...
Needles to say,service work was finished and he drove to the nearby Mercedes dealer and PX'd it for a C63 AMG
My other friend owns an M5,and its considerable cheaper to run the the GT...
Lovely cars and beautifully made,but depreciation and running costs are the BIG downsides..