RIPE, APNIC and other such organizations only sell IPs to members. To become a member you need to be an ISP and justify the use of those IPs by showing a concrete business plan. Not to mention that most of them only sell in large quantities like 1024. Read in RIPE's faq: http://www.ripe.net/info/faq/rs/general.html Maxmin probably rents them from a bigger ISP. The is usually what you do. When you actualy own your IP it's a bit of problematic because you still have to negociate with all your upstream providers to route your IPs, and some of them will plainly refuse and encourage you to rent from them.
I am not looking to buy IP addresses. visit http://www.maxmind.com/app/city and you will see what I am talking about.