  We consider a fixed-price mechanism design setting where a seller sells one
item via a social network, but the seller can only directly communicate with
her neighbours initially. Each other node in the network is a potential buyer
with a valuation derived from a common distribution. With a standard
fixed-price mechanism, the seller can only sell the item among her neighbours.
To improve her revenue, she needs more buyers to join in the sale. To achieve
this, we propose the very first fixed-price mechanism to incentivize the
seller's neighbours to inform their neighbours about the sale and to eventually
inform all buyers in the network to improve seller's revenue. Compared with the
existing mechanisms for the same purpose, our mechanism does not require the
buyers to reveal their valuations and it is computationally easy. More
importantly, it guarantees that the improved revenue is at least 1/2 of the
optimal.
