First let me say that DVDtracker is absolutely correct. (So the status quo probably isn't going to work)
But there are some things you could do yourself to drastically cut down on your bandwidth usage.
(I'm not entirely sure that the webcam is solely responsible for your bandwidth either. You've got a ton of large pictures in the gallery that I'm sure everyone who browses the site clicks on and costs you the bandwidth.)
Examples:
1-do you really need an update every 30 seconds on the stall? (yep, it's still a horse ;) How about once every 5 minutes, etc.
2-get to work re-saving all those horse pictures and this time set your jpeg compression to something like 85%.
3-Cut the images down from 640x480 to something smaller. The picture 'star1.jpg' is fairly grainy to worry about saving at larger image size, and if you resample it to a smaller size, it'll probably look sharper. The image 'jimmy1.jpg' is a good example, the image is smaller (only 25% of the size) but you can still see everything you need to see.
4-for some of the images, do they really need thumbnail links to the larger image?
5-you could consider using a service like [url]www.pbase.com[/url] for hosting your galleries, but it sort of takes away from the site. tough call.
6-in looking at your message board, it looks like you have a fairly active site so you're probably just stuck with relatively heavy usage. (Sometimes it stinks to be successful! ;)
I personally think your image galleries are your major usage concern, take a look at that and see what you can do about them.
Good luck!