Every seat I've bought in AZ wrecking yards has dust in place of the foam cushions. The foam doesn't last in the heat.
Watch a couple of YouTube videos on seat repair. New foam install is pretty straightforward. And you get to buy "hog ring pliers"...
I glued a block of new foam in where I had carefully cut out the old.
Carved it to mirror the opposite side. Had the cover repaired. Ran it through the washing machine and then reinstalled.