check craigslist or whatever you have locally. Out here there are always new vehicle takeoff offered and there also a lot of independent tire sellers. Yes I know the costs are high as I had a bridgestone with a slipped tread over $1000 to replace all on rear with 1 being adjusted out. Had a tire separation on my F350 a couple of years ago tore up the bed on truck, called bridgestone who recommeded I go to their tires since its used mainly on highway. Again over $1000 with all being adjusted out per the manuf with the shop.
SO just need to shop around or travel out your area for possible better deals.