Each one covers a specific year
For example, my 88 FSM covers all 88 EA82 cars except the XT
I no longer have an 88. I have an 87, but the differences between the 87 and 88 model years is negligible
As far as price goes, it just depends on where you get it. I got mine used and in great shape for $40 ($30+shipping)
I have seen them go for over $200 as well.