Equivalent trade. It was the law of alchemy and all alchemists followed it. Especially Edward Elric, the Fullmetal alchemist. In fact, Roy didn't know of any state alchemist or any alchemist really, who was devoted to the law, as Fullmetal was.
Afterall, Edward Elric was all about equivalent trade.
He followed the law faithfully and even applied it in daily life. Not many alchemists did. Fullmetal always did go the extra mile.
Roy frowned slightly and picked up a photograph, one of him and Fullmetal being civil. Hughes had taken it.
Sometimes equivalent trade was just not enough.
Shame.