When you are selling online, the customer cannot touch, feel or look at your product from multiple angles. Your product is stuck in a 2D state on the screen. So when asked how important is photography for selling online, I reckon it's probably the most important aspect of all.
Here is a sample case study.
This is the new photo of the necklace.
The new photo is simple and direct, I did not try too hard with the set-up, and it shows the product clearly. It took me about 1 minute to lay the necklace on a piece of paper and snap the picture. :)
Visual impression is the most important for online purchases. If you sell commercially mass produced items like stationary, books, displays or even supplies, the buyer probably already know what quality product they are expecting. That is why you see loads of disastrous photos on eBay.
But for handmade goods it is a different thing altogether. These products are handmade by you, you and yourself only. (okay, admittedly the necklace above can be easily replicated) But you get my point. Your products are not something out there in the market that the buyer could easily relate to and have quality expectations of. You need to give the buyer a strong visual impression to lure them to click on your item, and hopefully purchase it! People say that the first impression is the strongest, it cannot be true enough for handmade items. If you look at my sold listings of the necklace above, only the first photo is a new one, the others are still the old photos. And yet the sales stat is so drastically different.
I dare not say that I am very professional with product photography, but I do try and improve. Experiment on new techniques, take from a different angle, try different set-ups. Need help on photography? Check out Etsy's comprehensive list of photography tips right from how to choose your camera to how to edit your photo. :)