IMO, sheets definitely make a difference. I don't know about Ebay sheets, but I've bought MANY sheet sets over the years. After getting my new bed I needed sheets with deep pockets but didn't want to break the bank. I tried Springmaid sheets from Walmart and cannot express how much I love them. I was shocked at getting such quality sheets at a low price. They are heavy, smooth, very generously made and totally delicious feeling. I got the separates, called "My Carefree Sheets" for $15 each for full size, and I swear I'll never buy another brand! They wash wonderfully and in fact feel even better after laundering.
These sheets are 300tc, but I believe that higher thread count does not necessarily guarantee better feeling sheets.