Hi
I have an online business (my very first project) that now averages 3K visits a day or more. The retail sales I do are my own products, but mostly do Adsense and affiliate sales (which is nice, because it means no back end work for me.)
I think you are going to get a wide range of answers to your question, because there are a lot of ways to go about what you want to do.
I use SBI! (Site Build It!) and pay $25 a month for everything, including having the ability to let other people create pages on my site - called Content 2.0 - which has added close to 3,000 pages for me. My site is very active and growing, with fresh content being added daily. (Search engines love that.)
SBI has no restrictions on bandwidth and speed is never an issue. They also have unsurpassed support both technically and learning-wise. I learned everything from the bottom up through SBI and having everything, including having incredible keyword research and SEO tools at my fingertips.
What I pay is very, very cheap, I think, for everything I get. Matching apples to apples, this would cost $100s per month and features like Content 2.0 aren't even available anywhere else - unless you're extremely talented as a programmer or paid someone to build it for you. (Which would be $1000s)
But that's me. There are hundreds of variations, services and add-ons available, though. So what you're asking is not really a straightforward answer, I don't think.
