In Japan broadband is "flat-flat" rate -- i.e., no volume-related IP service charges, and no time-based facilities fees, just a straight monthly subscription fee -- with the speed/capacity largely varying by medium (copper/DSL, HFC/cable, FTTH).
In Japan as in many other economies that would have to wait for full unbundling/structural separation to achieve the competitiveness boost that the US enjoyed as a result of the Telecom Act of 1996, metered dialup was the dominant (and very expensive) access method until 2000.
DSL and cable internet access were available but pricy until mid-late 2001, when Softbank/YahooBB jumped at the opportunity to capitalize on Japan's new (actually, second attempt) access and metro facilities unbundling mandate to deploy super-fast, super-affordable DSL. Looking back at some old press accounts confirms my own personal recollections
-- e.g., according to Ken Belson ("Fast Connections Catch on In Japan", International Herald Tribune, 6 May 2003):
"In a contrast with South Korea... most Japanese providers have piggybacked on NTT's optical fiber network rather than build their own. That was made possible because of industry pressure on NTT to lower its fees for others to use its equipment. Once that happened in early 2001, prices to consumers fell by half and the number of subscribers soared."