However, if you have a look online, you'll see that there are two different prices for the rail passes - a "green" pass, and an "ordinary" pass. You might be asking yourself what the difference is, and what's behind the increased cost of the green pass variety.
The green pass allows you to sit in the green cabins on shinkansens. What this means is essentially the business class equivalent of what is otherwise an economy ride. You'll also notice that the seats in the green car cabins are in a two-by-two format (the regular reserved and unreserved cabins are usually 3x3).
The green car seats also boast more reclining space and leg room, so if you want to catch some Z's as comfortably as possible while you're getting from A to B then you might want to pay the extra.
In comparison, this is what the standard car setup looks like. It still has more legroom and comfort than most economy class airlines, but this is the cheapest cabin version on the shinkansen.
So is the added cost worth it? It's a weigh-it-up scenario. I think if you were traveling with kids and wanted the extra space to sprawl out, then the green car would be worth paying for - when I recently traveled on the shinkansen in a green car I was literally the only person in the cabin at the time! Generally speaking though, if you want the most bang for your buck, you should definitely find that the regular pass is sufficient.