Absolutely, and I'll freely admit that I don't know how to calculate that. I made a major assumption in my last post, that I'll explain here:
Most quotes I've heard recently put the cost of bandwidth at around 1-2c/GB. I assumed, quite possibly erroneously and I'll go hunting for the source in a moment to confirm/refute said assumption, that when TekSavvy's CEO said that a conservative estimate (read: "highest reasonable estimated price") of bandwidth could be 30c/GB, I was assuming that he was taking things like administrative costs and possibly infrastructure costs into consideration. I made this assumption because of the extreme disparity between the two cost points - 1c/GB from some versus 30c/GB from him.
I realize that I didn't make this clear in my original post - I didn't even hint at it, actually - so I apologize for that.
Also, when I just now checked my wording in my original post, I noticed that you edited your comment to include a back-of-the-napkin estimate of Bell's incremental cost of delivery to be around 13c/GB. In my opinion, this only strengthens my assumption, since I sincerely doubt Bell would provide additional bandwidth for less than cost.
Looking at Bell's website right now, I see that their "Performance" plan in Ontario lists 6mbps speed with a 25GB cap for $31.95 per month.
Using your calculation of cost of bandwidth being 13c/GB, this means that full utilization of the cap would cost them $3.25 per month, leaving $28.70 for administrative costs and upgrading.
In a completely unfair comparison, I'll mention that Rogers charges me $6.95 per month (last I checked, anyway) as a usage fee/basic fee/system access fee. Let's nearly double that up to $12.72 (to make the next calculation easier) and call that the cost of doing business (tech support, paper pushing, general administration). This brings the total up to $15.97 a month, which is HALF of what Bell charges for this plan.
Bell then gets to choose how much of their 100% profit they want to use to upgrade their network, and how much they want to use to give their CEO a raise.
As far as the overage is concerned, let's note that when I called bandwidth costs 13c, that was on the assumption that Bell made no profit from their "insurance" option. Anyone who doesn't pay insurance gets to pay $2/GB, of which at least $1.87 is pure profit. Their overage would be 1538% of cost - a nice markup.
Edit: I just noticed[1] that the true cost of this plan is actually $41.95, but they offer $5 off for the first twelve months and an additional $5/mo discount to be used towards their satellite service. I'm not going to bother doing more calculations, but I thought it was worth noting.
[1] http://www.bell.ca/shopping/jsp/pageblock_styles/Pricing/fle...
(I had to disable JavaScript to get that link. The JS-Enabled version requires you to drill down two links to get the full details to appear, so it was impossible to get a direct link to the JS-Enabled version of these details)