New United boss Louis van Gaal said on Friday he will monitor Strootman's recovery from a serious knee injury before deciding whether to bid for the Netherlands and Roma midfielder.
Garcia recently vowed that Strootman would remain at Roma this season, but just to make his point perfectly clear, he said on Saturday night that a huge fee would be required for the Italian club to even consider letting the midfielder go.
"What can I say about the rumours (about Strootman joining United)..." Garcia pondered with a smile after Roma's 3-2 defeat to United on Saturday.
"Maybe after a three-digit offer (i.e. 100 million euros), then we will sit down and think about it."
Strootman, who Van Gaal knows well from his time as Netherlands manager, missed Saturday's game in Denver as he is continuing his recovery from an anterior cruciate ligament injury he sustained in March.
The 24-year-old is making good progress in his rehabilitation, according to his manager.
"Kevin is following a normal recovery programme. He is fine. He will start running soon," Garcia added.