I am working on a paper that requires a comparison method to be implemented. The method of choice is not in my discipline. I asked a collaborator, who is an expert in the area and with whom I have several papers published, if he could implement it. It is about a week worth of work, most likely less. Both the collaborator and his professor would get an authorship on the paper.
His professor said that the project can be only done if I had funding for him. The collaborator is already funded through an external fellowship. The project does not require any purchases. Is this an unusual request?