I would agree with some of the previous comments. Your site's ability is directly related to your ability to sell in person. If you can't do that well...and use your site as an extension of that...your website isn't going to change that.
They are a great tool to expand upon your sales pitch from other areas where space or cost is prohibitive, allowing you to convince a potential customer that you are the place to buy long before they contact you. Essentially preselling before they ever get to you.
That's efficient and effective.
24/7 availability with automation.
Unfortunately, many sites are neither. Those who focus on selling and the conversion, instead of just raw bulk and meandering information, are the ones that will likely have more success using their websites, making their websites have more "worth".