[obrienmd]

Note, I haven't been in this world for a few years, so this info may be out of date

Actually, a heck of a lot more than that - WDM (wavelength division multiplexing) can give you 40Gbps (or more, though cost per bit per second starts to increase substantially) _per wavelength_, with 40 waves per strand (again, more possible, but cost-effectiveness not as good).

So, 1.6Tbps per strand fairly cost-effectively, with more physically possible. That 32-strand cable could carry 48Tbps with a config like this.

Upstream bandwidth isn't really expensive if you're selling to eyeballs (i.e. those who primarily consume services rather than provide them). However, as you said the fixed cost of laying fiber is non-trivial, as is the endpoint equipment to terminate all these waves and do something (route, etc.) with the transported data.