I don't know about your last line. Despite there now being more online selling platforms than ever before, eBay fees keep going up (or they find new avenues, eg postage, to add a fee). I suspexct my (and many others) dwindling eBay sales are a result of buyers having so many more options. Once upon a time eBay had the monopoly on online sales but with the likes of Facebook, Etsy, etc, etc they must be  constantly losing part of the market share- which reflects in lessingning sales.