Working in management at a retail store when Tiger was released....
The day of, we had "drop-in packs" that were just CD/ DVDs of the OS with standard legal booklets that we put in every single computer stocked in the store.
On the day of, customers would buy the computer and have to upgrade to the latest OS manually.
It was a couple of days before we started receiving machines with the new OS preinstalled. Honestly, I remember selling one of the Quad-Core G5s 4 weeks later that still had tiger installed w/ the drop-in kit. the machine was close to 4 grand so it just took a while to sell.
My guess is. buy a computer today, go online and pay the $9.99 for the up to date program or buy a computer on Friday and get it for free as a drop-in. wait until next week, get it preinstalled.