Right, and that consumes about 32Kbit or so with the overhead, right? It is ~8Kbit for the data and ~24Kbit for the overhead. This meshes with the G.711 being ~56Kbit for the data and ~80Kbit overall as the headers are the same.

There are plenty of other codecs out there but for someone looking at a commercial service as the OP is I think that the codecs in use are going to range between G.711 and G.729 with not too much else out there at either the high or low end.

Yes, there are plenty of other codecs in use in the world, just not particularly for what the OP is actually asking about.

Oh, and I've been in the business a while, too. ;)

With the caveat that there is also a lot of G.723.1 out there, I agree. But I do think that "HD" codecs are going to become more popular, especially in the US.