ITER is just a demonstration system, it will hopefully produce a modest energy surplus. As just one step towards an actual useful fusion energy source, Its a proof of concept and it's cost need to be considered in the context of the whole endeavour.

The new collider will be a fully functional 'production' system that we fully expect to probe new physics, and test specific scenarios that will require it's particular capabilities. It's an end product and the latest in a highly successful, proven series of systems. By itself that doesn't make it worthwhile, but I think a high cost for a final system is a different beast from a high cost from a test project.