Well first things first, the Boba Fett offer is a printed logo not a sticker so it will have a corresponding printed offer on the back of the card. This means the Obi-Wan Kenobi will be your 21 back figure and the others will be 20 backs.
Next issue is the condition of the packaging and it's not easy to make out from the photos but there are some areas that are a cause for concern. All the figures appear to have suffered from water/damp damage and both the Luke and Han have visible mould and it may be present on the Death Squad Commander and Obi Wan but it's difficult to tell. There's a variety of card warping, significant scratches and print loss to the cards, bubble dents to at least the DSC and Luke and possibly the other two as well.
The Obi Wan is looking like the nicest of the lot and depending on whether he has mould on the card or not might be worth picking up. As for the others, if they have mould on them I wouldn't want them anywhere near my collection! As for value check ebay for completed auctions but personally if the Obi Wan has a slight bend in the card but no mould, no bubble dents, no creasing in the card, then I'd probably look at around $200-$250 for it.
With the others if there is mould inside the bubble I wouldn't pay more than $50 tops for them because if it hasn't already happened that mould is going to stain the cardback and probably the figure and there's not much you'll be able to do about it. You may be able to salvage them and kill the mould without damaging the card and figure but there's a big risk involved. If the seller tells you it's simple and easy to do then you have to ask yourself "why didn't he do it already"? There's a lot of other nice carded figures available out there so don't waste time on the lost causes.
$1800 for 6 figures works out at $300 a pop. Again, check the completed auctions on ebay and see what $300 will get you as far as carded figures goes. Certainly much nicer condition that these.