The amount seems within reason to me.
The NSX was a sales failure. Sure, the plant allowed Honda to sell the very successful S2000 and was a technology incubator. But, ultimately, you have to sell cars to get return on that investment.
And, Honda simply didn't do that. Honda could have gotten the VTEC into the freakin Pilot and whatnot without the NSX program or Tochigi.
The NSX lost money, period. And, Honda will not produce another supercar. The reason why? Because the market has already proven that they will not make a Honda car in Porsche's price space a sales success no matter what its attributes are.
At release, the NSX was dramatically superior to the 911 and 348. Even after the redesigns and releases of newer 911s and the 355, the 3.2 NSX remained a superior car. But, it never sold like it.
Manufacturers must recognize their pricing niche. Acura cannot command the same price as Lexus, who in turn cannot compete in BMW's space or MB's. And, BMW, in the premium big car space, simply cannot command the same sales of the 7 vs. the S-class at the same price. BMW is just not perceived as at peer prestige as Mercedes. And, when Lexus crept its ES up in $ to where good 3-series cars were, they learned that they are just not perceived as the same prestige as BMW.
The "just a Honda" rap hamstrung the NSX throughout its lifespan as if "just a Honda" is pejorative. Honda was utterly DOMINATING Formula 1 and every other racing genre they entered, yet the NA market would not afford them premium respect. But, that's just the way it is.
The Z8 is too expensive for a Bimmer. So, people don't buy it. At $125-140k, they buy Ferraris. BMW cannot compete in that price space. Even Porsche really cannot. Honda could sell an "ultrasupercar," for $500,000, like the Enzo or Carrera GT, but they'd be selling like 10, just like everyone else who makes cars at that price point. But, car sales for profit are a volume game and every manufacturer has their niche. Porsche owns the sports car space from 65k up to around 120k. Beyond that, it's Ferrari. Jags can hang with Benzs in the midsize segment, and so can BMW, but in the large saloon class from 70k-150, it's MB and nobody else. Beyond that, it's Rolls and Bentley. And, it's incredibly difficult for mfrs to break out of these pigeonholes, thus the very existence of Acura, Infiniti, Lexus, and even Maybach.