Before revision:  We show that in a differential pricing regime 1) a CP offering low QoS can make more revenues than a CP offering better QoS through sponsorships. 2)  QoS (mean delay) for end users can degrade compared to the case where no differential pricing is allowed .
After revision:  We show that in a differential pricing regime 1) a CP offering low QoS can make more revenues than a CP offering better QoS through sponsorships. 2) Overall QoS (mean delay) for end users can degrade compared to the case where no differential pricing is allowed .