I don't think GHM hotels and Amanresorts are comparable. All the Amans I had the luck to stay in were something far above and better than any other luxury hotel (though with some slight nuances depending on the resort).
I stayed at the Saujana in Kuala Lumpur a few years ago and (for the price that I payed) it was more than fine, but simply a very big hotel in a beautiful garden, with many restaurants, many people, a professional staff, but nothing more than that.
Also the Chedi in Milan (which I have never had time to visit since it is so far from the city centre) does not seem to be comparable to other top facilities in Milan (e.g. the Bulgari with its amazing garden, restaurant and spa). On the other hand, as far as I remember, it is significantly cheaper.
Isn't GHM simply focusing on a different target client?