Abut ten years ago I visited a second-hand bookshop to collect a book I had bought from their online advert (I think it was abebooks).
The bookshop was stopping as a shop and continuing online only.
The owner told me for every 1000 books online they would have about one enquiry a day.(this was about ten years ago)
I often wonder what sort of living could be made entering details of 1000s of books online and then packing and posting ...