The last time that I know of when one of these came u for sale was in 2004. And it sold for £3k
The time before that when one sold was in 1999. It was in a Vectis auction. Set of 3 30 backs: Fett, Han Bespin and WBG I think. Went for under £300 I believe. So it went from around £100 to £3k in 5 years!!
God know what one would go for considering it been another 10 years!!
Palitoy is on a high at the moment, Fett is a popular Character and 30 backs still have that mythical status.
So you get a couple of heavy weight Fett collectors going for one, plus some Palitoy collectors (most of who I know of are looking for Fett and have been for a long time) and you could be talking serious money. I think more would go for a Fett that for a VCJ. But that could just be my bias!