Were their tobaccos really that good or it just another case of unobtaninum makes people nuts?
The answe is: yes.
They were known to use excellent tobacco, as many sellers do now. But there were some years crops and suppliers that are no longer available, so that helps add to both rarity and desirability.
I suppose the age on them also helps in some cases, because you know you're getting some excellent tobacco that's aged.
The unobtainium factor definitely adds to the price, and the quality feeds into it.
That's my experience, anyhow.