Odd message when trying to buy the 3TB after just buying the 1TB item :
"Buyer Requirements error
Sorry, you are not allowed to purchase this item
This item is only available to buyers who have not purchased 1 or more items from this seller in the past 10 days.
You can contact the seller for more information, or find similar items offered by other sellers."
Seller has 100% Feedback and has been an eBay member since 2010.
eBay Buyer Protection has always worked for me.