Re: How much is a IPv4 address worth
You are confusing "static IP" (or conversely, "dynamically allocated address from a pool") with "NAT".
You are almost certainly using NAT. If the IP address on your PC's network card (shown by e.g. "ipconfig /all") is different from the public IP address you're using on the Internet (shown by e.g. visiting www.whatsmyip.org) then you are using NAT.
Now, "static" or "dynamic/pool" IP means whether the public IP address you're using on the Internet stays the same, or changes every time you disconnect and reconnect.
A dynamic IP address doesn't really offer you any "protection". Your ISP is still logging every time you connect/disconnect from the Internet and what address you are using at each time, so any malicious activity from that address can be traced back to you.
And in any case, if you have a stable DSL line and don't power off your router every night, you are likely to stick with the same IP address for days or weeks at a time.
And Demon/Thus is very much an oddball here, by giving a static IP address. Most ISPs won't give you this unless you ask for and/or pay for it. Many don't even offer it at all.