Items that are sold by individuals on Amazon can have crazy prices. I've seem some common G3 ponies on there for $50-$100+, when you can easily buy the same pony on ebay or here for around $3. I've also seen some reasonable prices, and even a few bargains. It's all up to the seller, and some sellers are a bit more realistic and reasonable than others.
I tend to check ebay for more accurate pricing. Check completed auctions that actually sold. Some sellers set their prices too high, and those are the auctions that just keep cycling over and over again on ebay. The sold auctions is where I look for accurate prices, the crazy priced auctions are what I show my dad when he thinks he's made a thrift store find:p
A quick ebay search of "Goodbye Yellow Brick Road 1990" shows a few completed auctions ending in the $5-$8 range. There may be international editions or special editions that are worth more. International editions in particular can go for big bucks, especially if they contain rare bonus tracks. I don't know if this album has special versions or not. There seems to be a deluxe version released in 2004 as a 30th anniversary edition as well.