New seat foam?

So I pulled my seats and carpet out to do some RAAMmat sound deadening and I noticed the foam is completely disintegrating on the driver's seat. There was a pile of crumbling foam under the seat and if you push on the foam bits will just come off in your hand SO I need a new one (the seat has gotten more uncomfortable over the last few years and I guess I know why). I looked around some and OEM for an '02 Sierra was like $150??? Is that normal? or am I missing something?

Any suggestions? Thanks!