I don't -- just trying to apply some logic.
Apple has been working on 10.9 betas right up to the GM declaration (the idea that they've had a GM sitting around for weeks makes zero sense, given their own cycle of "here's the next beta release, it fixes xxx errors").
Let's say that they want to have 1/2 million MBP's in stock and/or ready to ship (from China) on release day.
With two weeks notice (~time from GM to 10/15), that's 35,000+ machines per day (or ~1 every 2.4 seconds) being loaded with OSX 10.9 (a quick, but not instantaneous transfer), placed into packaging and sealed, placed onto pallets and into transport containers, shipped (air shipping the initial production) and distributed to retail stores.
Even with the Chinese factory staff being flogged 24/7, I don't see how they could provide the needed volume of machines with 10.9 installed. Ergo, 10.8 with a free upgrade. Also ergo, if they announce 10/22 with later availability, they can be expected to ship with 10.9, as they'll have enough time to load the GM version before packaging.
Here's an interesting link on purchasing power parity with a few indexes showing how pricing vary around the world, and these figures take into account the difference in income vs cost of goods in said country, or the "law of one price" - if that works... (Guessing it's often quite wrong.. but it's interesting reading!). In my case, for Norway, by the big Mac index Norwegian goods should cost up to ~80% more than in the states. But if the law of one price holds true and I've understood it all correctly then the difference in avg salaries should balance that out.
