Sadly, selling items seller doesn't have on eBay occurs more frequently than I would like to see. This is not entirely scam from eBay buyer and seller relationship perspective, but clearly is against eBay rules.
As a buyer you lose your money for 1 month and your time (because you wait 1 month, do not receive anything, then have to order and wait again).
This happens because many sellers do not actually have or stock the items - they are middle men ordering from other sources. When items are not available, seller can:
- remove listing from ebay
- increase a price of listing 10-100 times
- fake a shipment(no real tracking number, maybe fake one) and refund after buyer (unsurprisingly) does not receive the item
There is some incentive to fake listings - it may be cheaper for seller to maintain fake listing than removing and adding a listing when stock available.
eBay rules are against it, but they are not strictly enforced. eBay is on the side which brings more money from fees (i.e. sellers). I would recommend to report such sellers and rate them accordingly.
Such selling practices ruins selling market for other eBay users, especially for private buyers and small sellers.
There are more topics on EEVBblog about similar eBay issues if you search around.