There must be information online about that. Just keep digging. Use different words and strategies in your search engine. You might happen upon something very useful. I'm confident that you will at the very least find a dollar range.
You can't have everything charged to the room and reversed because cash handling by certain staff - bartenders, etc - is something that needs to be shopped. So you will need to include those.
I wanted to cancel a shop yesterday because there was a Trump rally around the corner that was expected to make parking impossible. The MS company threatened to 'bill' me $350 for the income they would lose if I didn't do it so there you go, that's a nice sum.
You can't think of it like a regular shopper would in terms of fees, because you also would have to create some sort of report form (I am guessing Excel would work) for each department evaluated, and that would be time consuming when creating this document. You really need to factor in your time spent creating documents and then everything else.
I guess if all you had to do was write objective narratives for each department in Word with maybe a small subjective comment at the end of each, it wouldn't be too hard.