$20 is a decent price, I think, especially considering that it's OOP, but check eBay to see what they're selling for there.
The thing I love about that set is that it came with a nice book and has the original music from Jedi (lapti nek, ewok celebration) plus a few other bits and pieces that weren't included on the 1997 2-disc SE sets (although, the 2-disc sets also have a lot of unreleased stuff that wasn't in the anthology, too). If you have all the 2-disc sets and the Anthology, you've pretty much got a complete set of everything that was ever released officially.