The availability of mainstream or high end 3D cards has always been more or less random. This is at least true for retail cards that constitute a tiny minority. Basically, there have always been two problems: on one hand the waiting time between a product's review and its availability for sale can be between one or two months. On the other hand you have to consider the real and continued availability of those cards after this delay. This came to the fore during summer 2004 with the unavailability of the GeForce 6800 Ultra and GT as well as the X800 XT PE and XT.
Since then Nvidia has been using this state of play to its advantage by trying to systematically call for hard-launches, meaning the availability in online retailers at the same time as the reviews are published. It's a strategy that paid off in front of Ati's inaction, as they took more time before doing the same thing. The first problem was thus almost eradicated and it's a real improvement by those manufacturers. CPU founders and hard disk manufacturers should really learn from it! However, in regards to the real and continued supply, it's actually the opposite. As much as it's understandable (although regrettable) that the transistors monsters that are high-end chips may know some manufacturing difficulties, it's more detrimental that manufacturers launch mainstream products with excellent performance/price ratio knowing full well they won't be able to ensure supply. Yet today, although products based on G80 or R600 are available, those based on RV670 (Radeon HD 3850 and 3870) and even more so those using G92 (GeForce 8800 GT) are almost impossible to find or come with price tags far greater than those announced.
Unreal Tournament 3
Of course, the fact that the two latter chips use more advanced processes and are victims of their success explain the problem in part. However this new trend is regrettable. If the availability of a new version of the GeForce 8800 GTS (512 Mo) Compare Prices on 512 MB GeForce 8800 GTS Video Cards should logically make things worse, Nvidia claims on the contrary that it'll be the landmark of a new beginning for the recently launched cards. By the way, what is this new 8800 GTS really worth?