I don't know if this is every Staples, but I went to two separate Staples tonight and was told the limit on the Fee Free MasterCard Gift Cards was $2,000. At the first one the cashier rang up 9 cards ($1,800) and the last one gave a message of having reached the limit - I just said "that's fine, I'll just take the $1,800." The next Staples the kid asked his manager how many I could buy and she said the limit is $2,000. Same message came up when he tried to enter the 10th card. The manager came over and said to just ring the last $200 separately. She said, although it wasn't charging the activation fee the system was still counting it and thought the purchase was over $2,000.
Anyway long story to say looks like 8 cards isn't necessarily the max.