When I buy lifetime balance & rotation at AT, it has been only $19/tire (at least when I bought the tires new from them). I agree that if you pay for a one-time rotation every time you rotate, it doesn't pay off. I looked at the current set on the new to me Camry in my sig, and decided not to pay AT for a one-time rotation; I wasn't sure it would extend the life of the tires beyond what I'll get without rotating.
I'm not convinced that my tires need rotating every 6-8K; I measured the tires on one of my vehicles at 10K and tread depth was even. But I know the front tires on the Sienna were shot after 20K of not rotating. But the biggest point for me is that if I don't rotate when AT says to (every 6-8K) I don't qualify for the prorate, so I do feel that the $76 for four tires does pay off, over the long haul.