Based on a comment, it sounds like you're a reseller and your competition sells the exact same items.
Negotiate with your supplier You may discover your competition is getting a better deal. Ask the vendor if they have any influence on suggested retail pricing.
Improve your terms What are your payment options? Credit card only? Could you do 90 days? Hard to say not knowing your industry. What about return policy?
Pricing Could you offer better volume pricing? I'd bet you'd be willing to make a dollar profit on an item if you could sell a million of them at once.
Better Service Suggest other complimentary items. I hate to buy an electronic device and the sale clerk doesn't bother to ask if I need batteries.
I don't know your business, so it is difficult to make suggestions. Selling larger price ticket items sometimes require more personal contact. If customers just know you by your website, they have no problem leaving for better prices (unless your site just works do much better and you actually deliver on time). Is there an opportunity to educate this industry on what they should be looking for when they buy these types of things? If they learn to look for more than just price, you may win them over if you offer that and your competition does not.