That does seem pretty high. I was kinda annoyed when the sidewall on my $35 tires gave out after 3800 miles and there was plenty of tread left. I do overload them a bit though so I guess I'm stuck with that but even if I swapped both tires and tubes at that time $80 at 3800 miles that is $.02 per a mile? Which really still burns me.
I hope you misplaced a decimal place, and I didn't, or wow you are burning through those things.