Steve has made an astute observation. The process takes time, as he points out. But, it also takes skills, knowledge, space and, to a lesser extent, equipment.
Selling the five hundred pound Ampex MM1000 tape recorder probably presented the largest challenge I've seen, in terms of shipping. But even that was possible by using the uship.com website, which is essentially "Uber for stuff, with eBay style bidding." Recipient was ultimately happy with the item, shipped to Nashville.
For planning purposes, if a friend or family member is proposed as an agent, it's a good idea to estimate how long it will take, and even ask them to handle a few items to see how well the partnership works. Each item takes about two hours to handle: A half hour for the photography, a half hour to list it, a half hour for shipping, and a half hour for the final accounting. With help, about forty items per week is max speed, goal speed.
Peter