The Scarborough subway could be a poster child for the political hijackings of public transit. These preventable tragedies happen time and time again in Canada's largest city. The idea of serving the greatest number of commuters at the lowest cost is overpowered by politics, and replaced with schemes to spend more money on less transit, serving fewer people, more expensively.

This week, it was revealed that the cost of the proposed one-stop Scarborough subway continues to grow. On Tuesday, a city staff report pegged the estimated cost at $3.35-billion, up from $2-billion last year. The report says the final price tag could end up as much as 50 per cent higher. So we may be looking at a $5-billion, one-stop subway.

The staff report upping the price also reduced the line's low projected ridership; it expects to attract just 2,300 new riders a day.

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Globe editorial: Scarborough subway: Damn the cost, full speed ahead

The Scarborough subway is illogical transit policy. Its only logic is political. Politicians, municipal and provincial, get to tell voters in Scarborough that they're getting a subway – even though most of Scarborough is far from the line and its solitary station, the cost of which is impoverishing transit elsewhere.

It's the legacy of Rob Ford. He killed a plan for a network of far less costly light-rail projects across the city, while swearing that voters in neighbourhoods in line for light rail instead deserved, "Subways, subways, subways!"

Six years later, all Toronto can afford is "subway" – singular, no exclamation point. The Mayor, the majority of city council, the provincial government and the opposition are all fine with that.

The one-stop Scarborough subway proposal was born after an earlier plan for a three-stop Scarborough subway proved far too costly. The three-stop subway replaced a planned seven-stop light rail line – which of course would have reached more people, while costing far less. The light-rail line was to replace the crumbling Scarborough RT – a earlier political boondoogle, barely 30 years old, forced on Toronto by provincial politicians desperate to find customers for a Crown corporation's shiny new train technology.

Faced with the latest budget escalation, we eagerly await this story's next twist. Anyone for a $7-billion dollar, no-stop subway?