Yes, actually. However, because the railways in Japan by and large are actually private companies, a lot of detail just isn't released (or at least, not translated). Broad strokes however, because shareholders and government planning permissions exist, are released. As of 2017, the following was the expected breakdown, with construction costs not including rolling stock totaling ¥4.8 Trillion (~$43 billion US) of a ¥5.5 Trillion project.Any chance you've got any good materials on the cost breakdown on the Shinkansen line? Basically, the question I'm interested in, in this case, is what percent of the cost is the tunneling, and what percent is everything else (and, as an ancillary question, how important reducing the cost of tunneling is).
*However* it should be noted that this is still in the relative early stages of construction, with a crucial and difficult segment still not approved by the prefectural government. As of this April, they've announced an cost overrun of ¥1.5 trillion ($13.7 Billion USD, not accounted for above). Admittedly, they're going to the extent to underpin existing major shinkansen stations, which adds to the complexity, as does it's routing though some of Japans most varied terrain, requiring true deep bore tunnels. (Which, I should point out, completely bypasses the smaller but still substantial intermediate population centers already served by the Tokaido Shinkansen in favor of the straightest alignment between Nagoya and Tokyo, as that's already at capacity) I don't know how much of this, if any, can really be ported over to the NEC given the vast differences.
Frankly, I wouldn't be too surprised to see that soar over the next 7+ years of construction.