http://pages.ebay.com/help/policies/listing-bonus-prize-giveaway-raffle.html

A quote from that link...(emphasis mine).

For example, you can say, "I will throw in a state-of-the-art black and white TV if bidding reaches $150."

Is eBay really that out of touch with modern technology? :^O

BTW - there's a category specifically for Mystery Boxes. 😉

http://www.ebay.com.au/sch/Mystery-Boxes-/153545/i.html?_trksid=p3910.c0.m485