I just put my fourth cabin filter replacement in today...car only has 27,500 miles on it. I have been driving the same commute every day for almost 15 years, and have never had filters get as dirty as they get in the Sonata (both engine and cabin filters.) I could easily go 12,000-15,000miles in other vehicles before the filters were noticeably dirty and filled with debris. This car I am lucky to go 4-5mo/6K miles between filters before they are filthy and embedded with junk. Makes no sense.
Was at dealer today for state mandated annual inspection and a routine oil/filter change. Service advisor comes out waving my cabin filter and says "you need a cabin filter." I said "no, I will take care of that myself...that one is only four months old." He said no problem and put it back in. The filter was gray, but still had some bright white showing. Wasn't horrible.
Ten minutes later he comes out for a lady waiting for her Sonata to be serviced and says "Maam...you need a cabin filter and wiper blades." Her cabin filter was dark black and caked with debris. She agreed to the replacements and they charged her $55 for "Sonata specific" wipers and $25 for the cabin filter.
I stopped off at NAPA on the way home and bought a new cabin filter for $17.99. Had it installed 5 minutes after pulling into the driveway. Fit perfectly and was stamped "made in South Korea." I usually order the cabin filters on Amazon, but noticed the price has gone up from $8.50 to $12.50. For the extra $5 for the NAPA filter, I just decided to get it locally this time.
For those interested, this is what the dealer deemed requiring replacement: