I will do my best to address the questions. Note that most of the work is sold by the artists themselves and a fair amount of that is sold to their clients. In other words, we do not participate in many of the sales, so whatever I can add is anecdotal.
As a general rule, selling expensive artwork to collectors who have not see the work is a rarity. When you get above the 4k area, buyers want to see the work, for obvious reasons. So that is a case where you use the website as your main marketing tool to introduce new work to a new or preexisting client, its the first and most important step.
Brings up an important point. Always remember that a website is a tool and that it is something you need to use in your marketing efforts. I have been an artist for many years and can tell you that the best person to sell your work is yourself. I have had galleries, and others that have sold the work but you are the one who ultimately really cares the most about your career. Galleries and the others come and go, especially nowadays.
Incidentally, Artspan is, to my knowledge, the only provider of premium sites with user friendly and intuitive and complete search functions and directories that can bring a buyer to your individual site. There really is nothing like it, especially with our complete overhaul and redesign this past week. The individual sites are also elegant in design and lend credibility to the work shown.
I think where Internet sales are strongest is at the low end, hundreds of dollars rather than thousands. That is why we added the Prints-on-Demand feature. But the low thousands is also very doable, especially when the buyer reaches out to you for information because then you have a chance to connect on a personal level.... all those things count just as they do in the real world.
I am getting a little wordy, so let me close with this one thought. At the risk of repeating myself, as a professional artist you need a strong website, whether its from Artspan or some other provider... that will be the center for all your ongoing promotional and marketing efforts. Get it set up, learn to use it (we provide marketing help also) and make the marketing part of your regular routine.