Holy cow, 30-40 gigs/month? there is NO way I could ever use that much using wifi-tether. I remember one guy said that you shouldn't use over 10 gigs/month even with an unlimited plan as they could flag your account for review, and if they think you might be tethering they will get you for it. I think I'm going to go check my Verizon bill now and see if I have any charges.