1515
All the other brands went along
(slrpnk.net)
This is a most excellent place for technology news and articles.
If you have multiple ports driven off the same internal hub, they will share bandwidth.
You still need hardware significantly more complex than would be otherwise needed for a device for which USB 2.0 speeds were already much more than required.
I don't really understand how USB stuff works (what is the difference between a hub, interface, and controller?) but from what I've seen I think a hub supporting 20gbps would probably be in the 5-15$ range and probably not larger than a few centimeters