It's not new of course. French taxpayers paid for the blood thirsty megalomaniac Bokassa to have a self styled coronation as "Emperor" of the "Central African Empire". This is nowhere near as bad, but you may ask why, according to the Dominion Post, the Tongan government needs NZ$11.5 million a year in taxpayer aid from New Zealand when it can afford to spend NZ$4 million on a coronation of King George Tupou V. Don't forget Tonga is hardly a free country with liberal democracy with an open free media. Although the report says no aid money will be used, this is semantics - because if there was less aid money presumably the coronation would be cut back.
Even the BBC has the exclusive broadcasting rights - nice to see my TV license fee being used to pay for what is effectively a dictatorship.
International aid should be non-governmental, it should be voluntary. If you want to aid Tonga, then let reputable aid agencies develop projects and help it, and other poorer countries.