Are there loopholes when buying stuff on Ebay?

nope , xboxes have a recommended retail price , same everywhere as they cost the same , 1 or 100 and no discount .

eBay has a rule that you should not sell goods that have anything wrong with it (other than cosmetic flaws) under the "used" designation.   Any seller trying to sell something not working that doesn't designate the "for parts, not working"  can be forced to refund the money by eBay if something isn't right.   eBay is probably the safest place to buy used stuff (as long as you read the description carefully).  That said it's not Amazon so if you buy something listed correctly by mistake you can't assume it's returnable. 

That's not a "loophole." Sellers have to list the item's condition. The definition for "used" on eBay is:

"An item that has been used previously. The item may have some signs of cosmetic wear, 𝐛𝐮𝐭 𝐢𝐬 𝐟𝐮𝐥𝐥𝐲 𝐨𝐩𝐞𝐫𝐚𝐭𝐢𝐨𝐧𝐚𝐥 𝐚𝐧𝐝 𝐟𝐮𝐧𝐜𝐭𝐢𝐨𝐧𝐬 𝐚𝐬 𝐢𝐧𝐭𝐞𝐧𝐝𝐞𝐝. This item may be a floor model or store return that has been used. See the seller's listing for full details and description of any imperfections."

If you purchased an item that is listed as used, and it does not work, then you are entitled to a refund, because the item was not as described. 

https://www.ebay.com/pages/help/sell/contextual/co...

If it doesn’t work, then the seller must say that it doesn’t work. Otherwise, it’s assume that it is working. 

Up near the top right hand of the bid screen there's a link to contact the seller.  You can ask there.

Also, further down in the description it should say it's working, non-working or for parts only.

Ask the seller. If you are told that it works and it doesn't, you can get a refund.