Peter,
The other plant societies don't collect the plants nor do they decide on the merit of any particular plant. What they do is to make sure there are no duplicate names and collect information on the hybridizer and any pedigrees of the plants.
Of course the purpose of any society is not just registration but a way for enthusiasts to gather at meetings and receive publications on that subject. This could even be done as a totally email/ internet things so cost would be minimal. Even long standing societies like the American Iris society are doing e-memberships these days.
In the US we are SO spread out that this might be a better plan. In Europe the enthusiasts are much more concentrated. In Germany alone you could have a very active group.
Kevin
