I've never checked the tread depth for comparisons but my last set of Costco BFG's on my Tundra went 70,000km and I checked the depth when I sold them and they had about 40-45% total depth left (not usuable depth).
I got a ridiculous price from Tiretrands.com on a set of 33's, $1094.36 all in delivered to my door within 2 days from when I ordered them.
Vince