Joe Hockey has left the building. In his valedictory speech, delivered to Parliament this morning, the former treasurer said most people left politics due to defeat, death, disillusionment or disgrace: “We all have to work harder to leave [this place] with dignity.”

But if leaving Parliament with dignity means leaving it on your own time, as Hockey has done today, Australia could be headed for a very expensive new electoral system.

North Sydney voters will soon be going to the polls to choose a replacement MP, and taxpayers will likely stump up more than a million dollars for the privilege. (Last year’s byelection for the comparable inner-city electorate of Griffith in Brisbane cost $1,263,388 — and the cost of byelections is on the rise.)

In fact, with a federal election very likely to be held within a year, the special vote for Hockey’s electorate rankles. Hockey is capable of finishing his elected term. He’s quit Parliament now because he’s unhappy that he was demoted by Malcolm Turnbull to the backbench — and in all likelihood because he’s been offered a plum posting in Washington.

If Hockey really does need to urgently jet off to take up the post of ambassador to the United States, the seat could be left vacant until the next election. The other option would be for all sides of politics to agree not to nominate against the Liberal candidate — effectively allowing a replacement in the same way that casual vacancies in the Senate are filled by the incumbent party.

Of course, that’s about as likely to happen as it was that Hockey would swallow his pride and ride out the next six months as a backbencher. Farewell, Joe.