I spoke with USAA today and they quoted me the following:
4yr/100,000 for $1,761
5yr/100,000 for $1,993
6yr/100,000 for $2,647
This is for the comprehensive plan and there is not deductible for a claim. It obviously doesn't cover wear and tear.
If you want to get a warranty on a vehicle that is already out of warranty it is pretty expensive. For example, if you want coverage on a 2010 M3 Coupe it is $6,500 for the 6yr/100,000 plan.
Here is the link incase anyone is curious what it covers.