2001 Cobra brake pad thickness

If BOTH pads measure on each wheel measure that, I would say you are fine for at least several thousand miles. I usually replace mine when they are 1/8 " or when one gets down that low. 1/8" = about 3mm. Yeah, I'd say the dealer was smokin' you. But, I also would check them myself. And, you have to check BOTH sides, which means you usually have to at least take the wheel off to see that inside pad. I've often found that the inside pad may be thinner than the outside pad because the piston pushes against that one first.

Good luck.....

The Genuine Ford service manual for a 97 Cobra states 3mm service limit for both front and rear pads. I can't imagine it being much different for a different year. Sounds like they want to sell you a brake job.
I just got a set of high quality pads for my F-150 and they were slightly over 9mm brand new so an 8mm sercive limit sounds ridiculous.
Don't run them past the 3mm limit on the front because they won't shed the heat very well and might come unbonded from the backing plate, or worse, crack your rotor.
Hope this helps.

If you are using the cobra for road course use, 5mm is the discard thickness. Otherwise 3mm is discard.