There are two ways to answer that.  Our process will aim to solve your business problems.  You might need more customers; want to save time by answering fewer phone calls or more efficiently handling form submissions; or improving your company’s reputation.  You can then place a value on those things and determine if your website investment is worth it.
The other way is by calculating website Return on Investment.  Let’s say you pay $8000 for a new website.  Now think of how new sales you need to recoup the $8000.  For example, if your net profit on sales is 10%, that means you need to generate $80000 in new sales to pay for the website.  We recommend that you view the “payback period” the 12-24 month period after the site goes live.  But keep in mind an important fact: A new website must be effective to yield results.  If you open a beautiful new retail store but it’s on a side street and many people don’t ever see it, the effectiveness is decreased.  Still the concept is the same–you would calculate any of your investment over a period of time and compare that to results of the website.  If you’re interested in learning more about this, we love crunching numbers–just ask!