The other day I "borrowed" a bra from my sister in law, a 36C, and the cups are a bit small on me. Now I feel a LOT better. 36C, maybe D, is a whole lot better sounding than 46 almost A. Now I feel like I have actually made some progress with my NBE. Hmmm, maybe my wife has a point when she says they are big enough for her. But for me, not till they fill the 46A cup firmly. Funny how sizes change with band size isn't it? This makes me want to go to a dept. store and try on a few more sizes to see how I compare with the national average - 38B or C, can't remember which.

See my post on NB cup size. I wear a 38 band; a 36 is way too small. I suspect you have grossly overestimated your cup size. In terms of the volume off flesh, as opposed to the distance, it protrudes from the chest wall, it inevitably will increase with band size, the equivalent of a cup size per 2 inches, I reckon.
Finding the best bra for you does mean trial & error.

I wear a 46 band normally. I was just trying to get a bit of a psychological boost from trying the smaller band size bra and seeing myself fill out a bra cup sized larger than my normal A cup. The C cup bra I tried was filled out completely. However, my breasts are not fully developed to a mature breast. They have a stage or two to go yet, haven't quite decided which stage I am in. I am probably in a stage less than I think I am - or hope that I am. I am pretty close to what I want, just need a bit more volume to smooth out those wrinkles in the bra and I will be satisfied. At least that is the goal I have set for myself. I am in a resting stage right now so I can complete a physical and get some problems checked out. then I will resume my NBE and hopefully finish. But even so, it was a thrill to see a C cup filled out even if it was the wrong band size and probably just a AA in my band.