cheapest is usually neither degummed nor 1st grade.
Degummed is nothing but marketing hype. The best castor is Bakers AA, it is simply the oil from the first pressing. That is the beans are pressed till the shell is broken and compressed. After draining it is filtered and poured into containers. Baker's A is the second pressing, the beans are pressed as much as possible to get the oil out then filtered and poured into containers. The second pressing will contain gum and other impurities from the bean shell, it is not golden in color but slighty greenish. Nothing is done to Bakers AA to get rid of gum, but there never was any gum to begin with.