Do propane on-demand camp showers like the Kakadu Outback justify the price?

Only if instant hot water matters to you. Mainstream reviewers and r/camping threads agree the experience — true hot showers anywhere — is a step change over solar or unheated pump systems. But you're paying several hundred dollars, carrying a propane canister, and dealing with more setup. For weekend car campers, a solar bag plus a battery pump usually covers the same ground for a fraction of the cost.