Insurance under USA Wakeboard/NWL costs $50 per additional insured. The basic policy is $1M, but I know they did $2M for Dayton. If you click the right button on the online form one policy is good for the whole year!!
One important thing to note is that USA Wake board has deep and mature roots. There are a number of requirements that you have to meet before you can sanction an event. Finding a trained safety coordinator is key. You also need trained drivers. Getting trained isn’t something that can happen over night, well not unless you live near Chris Walker. If you plan now you should be able to train up a crew for next season. If you have questions let me know.
I strongly recommend working with Jeff Walker for surf events and Chris Walker (not related) for wakeboard events.
See the link:
http://www.usawaterski.org/graphics/downloads/2007%20USA%20Water%20Ski%20Insurance%20Fact%20Page .pdf