Rather than estimating a quality/price ratio, we prefer to concentrate on price/performance ratio. What's the difference? Well, the quality of an LCD display is in the eye of the beholder to some extent. It depends on who's using it and what they use it for. Someone who wants a monitor that can stand up to being carried around a lot, even if the performance is mediocre, will have a different approach to quality than somebody who wants a screamingly fast monitor but doesn't care much about its finish. On the other hand, performance is measurable. So our rating represents a kind of synthesis of the monitor's performance as compared to the THG benchmark.
There's no doubt that the VP930 is an excellent monitor, yet we're still a little disappointed. The difference between it and the 191b isn't blatant, except for the black level, which is visibly deeper. As for latency, it's also no revolution, and in fact it's a bit slower than what TN + Film can do nowadays. Obviously the video performance is exemplary, and the colour fidelity is close to being as good as the VP191b's.
Even if it's not significantly better than the 191b, the VP930 is an excellent monitor, at home in just about any application, that trades a slight gain in black level against a slight loss of latency.