The platinum plan can be had for about half the retail price if you buy it from the right person. I have a 2003 Tundra for which I purchased the plan earlier this year through a contact on Tundrasolutions.com. The dealer is in Massachussetts and I purchased the 7year/75,000 plan for around $700. Just make sure you do it before your 3yr/36,000 original warranty expires.
Go to tundrasolutions.com and look under the general tundra section and the information should be on a sticky at the top of the category. If you have any troubles, let me know and I will dig-up the contact information. One good reason to purchase the platinum plan, besides those mentioned, is that it is transferable for $50 and is a great tool for selling your vehicle to a private party.