And while Buck is disappointed to see Robben leave, he reckons the offer was too good to turn down.
The American said: "From a fan's perspective I am a little bit unhappy because Robben is a very good player and he's done some good things for Chelsea.
"But for reasons that you will have to ask him, he wanted to move on.
"We really didn't want that to happen but in football sometimes you have to do certain things and I think we struck a very good deal with Real Madrid.
"We've pretty much doubled our money, which is good football business.
"So we're sorry to see him go, but we've made a good deal and we wish him well."