It depends on what all you need to cover but here is an estimate. Assume about $10 per person if you have 200 or more people, but then add the general expenses. For example, my kids school walkathon, with about 200 participants, cost just under $2000. Note that we had no facilities or police charges. Here is a break down:

Per Person: T Shirt = $5.50 at most, Lap cards, lanyards, small prizes = $2.50, Miscellaneous = $2 Total = no more than $10 per person
Fixed:
Yellow tape and cones to mark the course = About $150 for a schoolyard event
Extra trash pickup or janitorial services= ??
Outhouses = ??
Rent, borrow or purchase canopies and tables = ??
Have concessions items donated or charge for them = net profit only
Do you need to pay for facilities or police supervision = Call officials who are associated with your site
Do you need to cover insurance or is that part of a school where the insurance would be covered (check with principal)?

Other readers, if you have expenses I haven’t listed, please feel free to add a comment. Thanks, Lee

Thanks