I read somewhere a few years ago about the statistics, India took about 47% of the H1Bs, China took about 17%.
India's IT agencies or staffing companies somehow get a lot of the H1Bs then offload some works to India, or fly in H1Bs from Inda to CA, don't know how that exactly works, but it does offer a lower H1B wage, maybe that's one reason they have so many H1Bs, I don't really know.
For most other countries, H1Bs are hard to get, and those individuals are normally hired by USA companies directly(not via a staffing agency or something like India's huge IT companies' branch office), these guys are paid decently and low-wage is not an option.
I'm trying to say the H1b-low-cost does exist for some cases, people abuse the system whenever they can. Meanwhile, many other H1B hires are paid the same as citizens, if not better, especially when they're hired by a local company directly.