Diversions are normally quite expensive too, considering the burn for the additional take-off and climb, (how much fuel do you think they uplifted in Adelaide?), Landing and handling fees etc. positioning of new crew, bad will from the pax, which will take a big chunk out of the $10,000. so would have thought it prudent to carry the extra, for the sake of maybe only $2-3K, (revenue from one First Class seat), aircraft and pax all in the right place and on time. Never worked for a carrier that, as normal SOP, didn't plan an alternate.