...does anyone know who was the first to make them in SL?
I mostly remember whose I first came across: the Rhenworks shirt, made by a sweet vixen whose name I am abjectly sorry to say escapes me right now; Kayi Laa's breasts, by far the most advanced of their time; Ittindi Gavaskar's fine work. But I have no idea who was the first. I'd like to know so I can appropriately honor him or her.
Of course, nowadays, there are many makers of prim breasts; we really do have it far easier now. I'm a newcomer compared to many, and I'm sure that there are many stories of way back when a lot of women made their very own prim breasts--and some still do. I have huge respect for them.