how much webspace and web transfer does a wecomic need
(lets say this web comic is pretty popular with around 3000 - 4000 members registered
and each comic takes bout 200 - 400 kb)
With any web space you have to figure in the size of the entire site, now much download in necessary to view the pages, how many people view the site, how often, and how long they move around. My entire website fits within about 3 MB (something I'm rather proud of actually) and I figure the average person is going to look at most of the things on it. So each person is going to need 3 MB of transfer. Now if I have 100 people look at the site, that 300MB now if they check it every few days... 900MB a week... It can build up pretty fast.
Generally though, you do not want to get a service that's a few gig of transfer or below. I myself have a service that gives me something insane like a terabyte and it's one of the cheapest I've found (About $5-$6 a month).
At the end of the day here's how you figure it, make a guess at how many people you actually expect to see your website on a daily basis. Starting out, 5 is a big number, but when you start growing, a few hundred isn't asking much. When you get big, a few thousand. Guys like Google get millions of hits a day. I wouldn't be surprised if it was in the billions. Once you have a number for how many people will visit you, try to set a number as to how much file size each person will need to download. Then take the two numbers and multiply them together. Then take that and multiply it by 31. That'll be your guess at a monthly transfer. Find a service that gives you more than that, preferably double.
Also remember to optimise you web content though, best way to keep your bandwidth down. That's why my site which is all my work is only in the 3MB area.