Before i finished reading your question i know it was a bad clutch and looks like the driver has been driving with his foot resting on the clutch pedal or slips the clutch when driving ,
Many possibility's for the clutch to wear down . 52.000 mile but also possible the Lad bought the car from a first owner that was the bad driver, and the 19 year old manage to get 8000 miles before failing completely.
Like said many idea of why the clutch is now bad .
With warranty on parts that wear are not covered ,brake pads, clutch ,tyres etc
What i would suggest is get a second opinion from another repair shop for a clutch job, as $3.300 is a expensive repair just for a clutch ..
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Kind regards Greg.