The professional will appreciate the business that you will be giving him. And it will be one less headache for you to deal with.
I wholeheartedly agree with your comment but I'm just trying to work out what a professional should charge for what should realistically represent about 20 minutes work for said 'Pro'.

If it was just to pop in the lock strips and assuming all the other work was done,for such a job I would most likely tell the customer to stick me on their Christmas card list....or to return the favour sometime.