The nominet costs you are looking at are direct registration, not becoming your own tag with electronic registration.
The £75 includes them doing all the data capture, sending certs etc. The more you register the cheaper it gets, so they are not selling at a loss just a very small profit, and small profits on many sales = ÃƒÆ’Ã¢â‚¬Å¡Ãƒâ€šÃ‚Â£ÃƒÆ ’‚£Ãà¢â‚¬Å¡Ãƒâ€šÃ‚£.
You need to become a member
http://www.nominet.org.uk/Members/HowToJoin/
£400
Then the costs of using the automaton
http://www.nominet.org.uk/Members/BenefitsOfMembership/
£5 per registration.
http://www.nominet.org.uk/TagHolders...iningATag.html
Looking at your post 3 you would need to be registering 160 names a year
400 / (7.50-5) = 160 before break even.
Unless you are selling loads of names looks like you are still better off using a third party.