What exactly is that meant to show? There's no label on the x axis. I only know it's meant to be a length of time as the 360 line is longer!
The X-axis is months. The chart is showing number of sales per system over time since their launch. You can get an estimate for when December/Christmas is on the X-axis based on the spikes in the sales numbers. I find it telling that in non-holiday spending the PS3 sells at the same rate as the 360, but when someone else is buying (as a gift) the cheaper system sells faster.
Quite a few people have less money now so Sony really should drop the price or they very well could start losing ground. If you are looking for a flat out gaming system spending $400 on a PS3 doesn't make much sense when the 360 is $300. That's two games right there. Or for the same price you can get a 120GB Elite 360 with Halo 3 and Fable II for $400. With more and more games being multi-platform it makes more sense just to go with the cheaper system if you are only into gaming.
If Sony could drop the price of their system, I think you'd really see there sales rise. If they don't though, I think you might be seeing them slipping around xmas time.
The problem with your logic is that Sony also has less money. They are just now possibly seeing profits from the console, and cannot really afford to lower the price until the parts and manufacturing become even cheaper. That is why many, including myself, believe that we will see a price drop when the 45nm chips come out.
And yes, while you can get the 360 cheaper there are features of the PS3 that some (not all) need that will cost even more on the 360, like Wi-Fi. The 360 requires a $100 adapter to use Wi-Fi. The fact that my Internet modem and router are a good 50 feet and a wall away from my TV is the main reason why I haven't bought a 360 yet. I can either spend money on an adapter, making it as expensive as a PS3, or drill holes and run unsightly cables. My only other option would be to put the 360 in the bedroom, where I don't have an HDTV.
Take someone like myself who realizes that just in order to have similar gaming capabilities will require an equal cost in the end, and then I look at things like the Blu-Ray player, the Internet Browser, and various other multimedia capabilities (My PS3 is filling with DivX files, complete with surround sound, so I can leave my DVDs on the shelf) and even if I was just looking at gaming the PS3 is a better deal, as it has value added for a similar price.
Now, all of that said, the PS3 is approaching its third anniversary. It is already bucking trends by having a launch similar to the success of the PS2, and maintaining similar sales to their cheaper, most equivalent competition.
But sales of game consoles have always seen 80% of their sales after they get under $200 (Wii may be an exception, only time can tell). If the 360 can drop the price of a console with a hard drive included (The Arcade has not sold as well as the HDD models) below $200 before the PS3 can get under $300 I do believe they will suffer greatly.
Now this is the part where I go into 100% speculation mode:
I think that time will be by Christmas. Microsoft knows that one more price cut could be a huge blow. I honestly believe that the way Sony is tying GT PSP to the PSP Go will be reflected with either a Slim PS3 or just a cheaper SKU PS3 model tied to GT5. However, I cannot imagine more than a $50 price drop, unless Sony is hiding just how much money a 45nm chipset will save them.
Overall, I do believe that Sony will need to have a price cut soon, but it does not need to be right now. The only thing that may save Sony if it isn't large enough is the wording regarding Natal on the 360 recently that has referred to it as a new console (a comment taken back after it was said). If the 360 keeps the price the same but includes motion control then Sony may have more time to get a PS3 price drop out. Assuming Sony doesn't do the same thing with their motion control, that is.
I was never trying to say that Sony is fine without ever lowering the price. I was merely pointing out that attempting to compares sales numbers to the 360 as evidence was incorrect. The PS3 has sold at a similar rate despite being more expensive. The only way it could have ever caught up in total sales was to have sold a years worth of extra consoles, and the only way they could have done that was to have a dirt cheap price and a system that pandered to old people and housewives.