The question has come up about buying IPv4 addresses from other folks once ARIN and others have run out of their allocation pool. The biggest question is pricing.
Organizations have two options. The can lease or sell you the IPv4 space. Selling of IPv4 space needs some clarification. You can’t just sell IPv4 space like you would a tangible good. If you truly wish to sell it, as in give up all rights to it, you actually have to transfer it via the Registry. In the U.S. we typically go through ARIN. This means if you buy IP space from someone you still have to meet the requirements from ARIN to receive that IP space.
What are some common pricing to expect?
There are several brokers out there, but very few publish pricing on recent sales. Since this is basically buying real estate it can be highly negotiation and sales driven. Given the current state of ARIN allocations this will only drive the price up.
One site that publishes data is ipv4marketinggroup
$12.50 per IP address for a /22
http://ipv4marketgroup.com/broker-services/buy/