I uploaded a large image. Then visiting the page. It correctly shows the information of the image (filename, original price and a purchase button).
But, it also show the image using the original image, scaled down only using css:
<img src="http://mysite.com/wp-content/uploads/sample.jpg" class="sell_media_image wp-post-image icon" title="" alt="" data-sell_media_medium_url="http://mysite.com/wp-content/uploads/sample.jpg" data-sell_media_item_id="810" height="428" width="640" style="max-width:100%;height:auto;"/>
It's too risky. Because visitors can simply right click and save it to their computer without having to purchase, they get the original full size image.