Yes, thank you.
There's a variety of different factors that come into play as to why some summits are more expensive than others. For example, if a host country picks a facility where they already have a structure in place to host the meeting, they won't have to spend money on erecting a certain facility. Broadband communications have to be taken into account. Also, there is the transportation of the leaders. For example, if you had a summit in Toronto versus having it in Muskoka, you'd be able to avoid the additional costs to get the leaders from Toronto to Muskoka. Most would fly directly into Toronto.
There are other factors in assessing a location--for example, security. Since 9/11, in particular, there have been efforts to have G-8 summits at more remote locations, because they're seen as more securable and harder to get to in terms of demonstrators. Again, these are the sorts of costs that come into consideration.
One of the major reasons Canada tends to have to spend so much more money on security is because we don't have major structures or major annual portions of our budget that are awarded to military structures. For example, when the Washington summit was held in 2008, they already had so much security infrastructure in place because of the everyday goings-on of Washington that they didn't need to usher in special summit dollars for such security measures.
These are all the types of things that come into play. I'm happy to answer more specific questions, but I hope that gives you a bit of an idea about it.