It’ll only cost $2 million.

That was the promise then-prime minister Jean Chretien made in 1995 when introducing Bill C-68, better known today as the federal long-gun registry.

Canadians of a certain vintage won’t need any reminder as to how things turned out in reality: the registry ultimately became a huge political albatross for the Chretien government, and by the time the Harper government ended it off in 2012, the tab had ballooned to a whopping $2 billion. That’s one thousand times the original pledge.

Fast forward to today, and once again a Liberal government in Ottawa is pledging to crack down on guns. After promising a gun ban and buyback program as part of its 2019 election platform, the Trudeau government immediately seized on the tragic mass shooting in Nova Scotia last April to ban a swath of “assault-style” weapons (a term which has no legal definition) and implement its ban and buyback plan.

That ban, which is now subject to several legal challenges on both constitutional and procedural grounds, was cynical enough. Accordingly, the Canadian Taxpayers Federation has sought intervener status in two of those challenges, arguing that taxpayers need to have their voices heard.

Even if it survives these court challenges, the ban, which effectively lists various guns based on how scary they look, won’t turn into sound policy. Even the National Police Federation, the union representing the Royal Canadian Mounted Police, says the ban is unlikely to curb gun violence. It points out the vast majority of violent crimes involving guns are committed with illegal handguns, many of which are smuggled in from the United States. Banning a different category of guns that are legally owned does nothing to address this problem.

Perhaps strangest of all is the fact that the proposed new buyback program is optional. Licenced gun owners can keep the banned guns, they’re just not allowed to buy, sell or shoot them. It’s quite the trick to argue in the same breath that these weapons represent both a serious enough threat that the government will buy them back, but also that it’s fine if people want to keep them.

If the ban is bad, the bill for the buyback might really end up being the worst part.

This week, the Trudeau government introduced Bill C-21, which, if passed, will make the gun buyback a reality.

Public Safety Minister Bill Blair has pegged the cost of the buyback at between $300 and $400 million.

But if the cost of the long gun registry taught us anything, it’s that vague cost estimates aren’t very reliable.

A buyback plan won’t be a simple matter of gun owners showing up to hand over their guns and Ottawa cutting them a cheque.

As with any government program, the layers of bureaucracy will inevitably be thick. A master plan will have to be developed. Each and every model and type of gun will have to be specifically and carefully identified. A database will have to be built. A public information program will have to be rolled out. Staff will be need to be hired to collect the guns. And all of this is before tackling the subjective question of what constitutes a fair price for gun owners.

Gary Mauser, a Professor Emeritus at Simon Fraser University, estimates that the actual cost of the Trudeau gun buyback plan could run as high as $5 billion and dwarf the gun-registry boondoggle.

Considering the federal government’s failure to deliver everything from navy ships to employee payroll systems anywhere near their promised budgets, Canadians should be rightly skeptical that their gun buyback plan will be any different.