Relisting a listing after it has ended doesn't carry over the purchase history. If you set up your preferences to use the out of stock option, a good till cancelled listing won't end when you run out of stock. Then when you add more stock, the history will remain on the listing. Go to site preferences to check off the out of stock option. Note that if you only have 1 of an item, you will have to manually end the listing once the item has sold.
