No, 7$ is very reasonable even for a /20. You don't buy IPs from brokers if you are serious.That's on the very low end. Perhaps if you bought a /15 (131,072 IPs) could you secure a rate like that ( http://ipv4marketgroup.com/broker-services/buy/ ).
Back in 2011, well before IPv4 exhaustion, Microsoft paid $11.25 per IP on a purchase of 666,624 IPs ( http://www.networkworld.com/article/2228854/microsoft-subnet/microsoft-pays-nortel--7-5-million-for-ipv4-addresses.html ).