They are high commodity. Because they were never used frequently there aren't many used ones available. And the few used ones people are willing to part with are still around $90. They hold their value well.
Morebeer in Riverside, CA, had a bunch of refurbed and used 3gal kegs inside their store. 65 for refurb'd, and 55 for the used/non-refurb'd. This was like 2wks so they may be out of them by now.
I think I got mine at morebeer when they had a sale about a year ago. They do turn up from time to time, and are usually about $70-$80 when you see them.