It's been about 10 years since I worked with a group to set up a show, but at that time, it worked like this:
A "show" would be a minimum of 5 corps (1 top tier, 1 second tier, and 3 open class). Top tier approx.$2700, second tier approx. $1500, open class approx. $900. I don't remember the DCI marketing fee and judges fees. The total for the smallest show was right around $10K. You have to have a venue that's large enough to cover your expenses which means you need enough big name corps to sell enough tickets to fill the stadium. Most local shows would run $15K-20K to host. The host has to put a percentage down, another payment during the spring (after ticket sales start), and the final payment must be made BEFORE the first corps steps into the stadium. As far as the "weather" issue, the host can purchase event insurance for a few hundred bucks and it is well worth it.