ehhh.. fortunately? For whom exactly???
In a competitive climate, for everyone. If nvidia make a great product, it sells extremely well, then both the consumer and shareholder get benefit. If nvidia make a bad product, it sells poorly, both the consumer and shareholder are hurt. This is really basic, but the reality falls somewhere on the shades of gray of these scenarios.
In the case you and Hans Gruber are discussing, nvidia only
need to lower their prices if their sales fall, because in reality, even if the AMD cards are better, nvidia has the mindshare and can overprice their cards a little more if they wish, and still make a healthy profit. Price them too high, and overall profit decreases due to sales decline. Price too low, the same happens because margin per card is too low.
However, nvidia may
choose to lower prices not due to a sales decrease, but to maintain marketshare and mindshare, thus hurting AMD's efforts to gain on them. Because nvidia has a lot of capital and market cap to work with, they can take some "hypercompetitive" routes to continued success against AMD. Such a strategy might not work against Intel, but they (nvidia) may consider it easier to fight a giant (Intel) when you don't have a yippy dog (AMD) nipping at your ankles.