I'd be dubious if they are expensive, as you say they are. Seventies japanese speakers aren't highly sought after, for the most part -- certainly there were plenty of excellent models, but many were only sold in Japan, and those that you are likely to see, like the Yamaha NS 1000s, were a lot more expensive -- Akai is known for tape recorders, not speakers, and the 155s (at 350 a pair according to Orion Blue Book) were in the middle of their offerings, so I'm inclined to think they are more or less Kabuki speakers, which you can find for less than large sums of money.
But really the only way you can tell is to hear them -- only you can say what you think sounds good, but its also true that there are a lot of products out there that none of us pontificators has actually heard -- only a small portion of components ever get reviewed, and though a much larger portion gets word of mouth, there are still many that are essentially terra incognita.
But I'd be willing to be that if no one pipes up to say these are the greatest thing since sliced bread, that, in fact, they are pretty average.