You're probably looking at around $20K USD for the website development (complete package, actual development company, plus the marketing, etc) alone.
$20,000 !? I built my website using HTML, and it did not cost a penny. If you get to grips with basic HTML, you can easily put together a website. After that, you will need to consider hosting it. If you already have a website, you cna add it on to that. Otherwise, you will need to buy a domain name and server space (unless you make an arduino web server). 1-2-3 reg seems a common web hosting company, so have a look round there to get an idea about prices.
As cr0sh said, professional web development would not be cheap. On the other hand, homebrew websites are.
Onions.