The group
"Ten Rings" was hired by Ironmonger to kill Stark, not capture him. They didn't know who he was. They failed to kill him but captured him at which point they were surprised who he was. They sent Ironmonger a message saying they were dissapointed he didn't tell them who it was. It's at the beginning but it's in Urdu or something. Ironmonger is a profiteer though, he wouldn't hesitate to sell them the weapons later once they didn't have Stark building them. Remember Stark was demonstrating new weapons, Ten Rings wanted the newest stuff, they already clearly were getting earlier stuff from Ironmonger.