Sears review: shocks/struts lifetime warranty

Went to Sears Auto Center in West Covina today to replace the shocks on my S10 Blazer, 25 years after first purchasing them. I have lifetime warranty but when Daniel was preparing my paperwork, he stated that my info was no longer in the system, the exact shocks were no longer available, & I would have to pay the difference. When Daniel called the parts store, I could hear the parts guy quote the price for the rear shocks, $29.99, but Daniel entered $79.99. He then quoted me almost $600.00! $600.00! I originally paid $26.99 per shock. I objected to the point that the manager came & took over the transaction but still was charged for the difference, to the tune of just under $70.00 plus $100.00 for labor. There is no language in the warranty that says you have to pay the difference, just that the shocks will be replaced for as long as you own the car. Is this how Sears does business? So disappointed and angry at Sears' & Daniel's completely unethical behaviour.