Here's an
article from 2016 about insurance coverage amounts and costs for Deshaun Watson to return to Clemson. Not sure if the rules have changed since, but a few items of interest:
1. This was a pre-season article so the costs for a single bowl game would presumably be considerably less.
2. The school was allowed to pay for the premiums.
If bowls are interested in remaining relevant, star power matters. They should be involved in negotiating and securing these insurance agreements for key draft prospects, offering a standard schedule based on expected draft position. Players could still opt out, of course, but I think there are potential solutions regardless of how large a problem any individual fan believes this to be.