What model are you downloading from specifically? THD units you are lucky to get around 8-11Mbps for PS downloads. So assuming a slow speed of 8 Mbps = 1MByte/sec => roughly 3.6 GByte/hour. S3 OLED units are faster than THD units (say around 13 Mbps) and Premiere units are much faster still (say 20+ Mbps). To benchmark download speeds try a download using your browser directly. You should not notice much difference between the curl download speed and your browser. If there is then maybe you have an anti-virus program or something throttling curl.