Everything you say is true, but on eBay, you can contact the seller directly if they didn't put in a shipping cost. Plus on eBay you can make an offer without commitment (if rejected)
Not putting in a shipping cost invites people to ask how much to ship the item and what the total amount will be. Sometimes the people decide on something else. It's just part of selling on the internet, whether it's Audiogon, eBay Craig's List or Facebook marketplace. There will be scammers (easy to spot), there will be people who ask and then stop responding. If you don't have a thick skin, selling things online may not be for you.