It's a level 8 ritual. Refined azoth is 100 gp per ounce and basically unavailable for sale ( although one party has access to an unlimited amount). The area of effect would be maybe a 50' radius. The problem would be finding enough mice, although I could see animal growth or enlarge being used. A single mouse is only worth 50 gp.
I might put a limit on the total value. My highest level mage from either party is 6th level so I have some time to mull it over.