Currency in Wallis and Futuna to CFP franc (XPF CFPF). For 9.9 US dollars you can get 1.02 thousand CFP francs. For 99 US dollars you can get 10.2 thousand CFP francs. And the other way: For 99 CFP francs you can get 0.962 US dollars.
And if the trip plans are simply for a given region of the world, then maybe it will come out cheaper than in Wallis and Futuna in nearby countries? See prices in: Samoa, Tokelau, American Samoa, Tonga, and Tuvalu.