I love hearing about other peoples experiences with “free” postage.
I sell on other sites as well as Folksy. On one site I sell only to the UK, so it’s easy to have postage included for each item. During July I sold 2 items.
On another site sales come from around the world, so I have postage prices shown separately. During July I sold 31 items in 20 orders - yes, the customers saw the advantage in buying several items at once to save postage. They would seem to have no problem paying from £2.50 to £15.00 postage for their order, as long as they can see why (e.g. Australia is further than Germany).
I personally never search for “free” postage when shopping, I look for free or discounted rates for multiple items.