Aren't those horses beautiful???!!! Okay, that makes it all worth it.
But to answer one of your questions Jetee, there were two distinct meetings. And yes, the cost is the cost of covering off the security & infrastructure to hold both of them.
The G8 meeting was held in the Muskoka town of Huntsville, about 2.5 hours north of Toronto in classic cottage country. That was from about Thursday night, and all day Friday.
The G20 was held in the city proper, at the Toronto Convention Centre, right downtown. This was done on the Saturday and Sunday (26 & 27th). The security actually included a 4 km long fence that was erected and bisected or separated the convention area from the rest of the city. The police's mandate was to prevent any compromise of this fence. A similar fence was erected in Muskoka for the G8.
I heard that there were tanks positioned at the airport. So there was definitely more than police on the ground in Toronto.
Incidentally, this is the first time that both meetings were held at the same time and place so that may have an impact on cost as well.