It isn't Bruce's money in the first place, and Tony had been able to talk him into helping create Ultron; he's not going to have much difficulty cajoling Bruce into giving him the credit stick for a Hulk doll, no matter how awful it is.

Maybe he can just "accidentally" forget it when they head back to Earth.

"I've barely even had a chance to be not gone and you're already planning for when I'm gone." He eyes the Hulk doll with all the pleasure and desire to cuddle that he'd give a cobra. "I guess I deserve that."