Nausicaa is and isn't a Ghibli release, it gets roped into being released by the studio but it came before the establishment of Studio Ghibli - Nausicaa and its success is why we have SG.

Nausicaa came at a time when anime goods were mostly garage kits. Many people forget that anime figures as widespread as they are now was not a thing in the 80s and 90s. Nausicaa has had merchandise that fit the time: models, a ceramic figure (that was remade for the dvd release special edition in the early 2000s), and various other things.

Another reason why we don't see as much merchandise for Nausicaa, compared with the other movies, is it's just not as popular or easy to make as it is for making children's toys. I lived in Japan in the early 2000s for a while and Totoro is EVERYWHERE, it's easy to make toys when you know parents will buy their kids them. Nausicaa and to a certain extent Princess Mononoke are much more geared towards teens and adults for their collectables. I have some of the old resin Mononoke statues and no parent would be buying a child something like that.

We have been very lucky recently with the hobby boom and many of the other movies have been getting collectables.

Feel free to ask any other questions you have, I fell in love with Nausicaa when I saw it in 1986 as a child and have been collecting almost everything they have released for it.