This should give you an idea of prices for all the SW characters that were released on Trilogo cards, obviously not all of them are first 12:
The first 12 figures that didn't get a true Trilogo release are the original solid dome R2, original fixed limbs Threepio, Power Droid & Death Star Commander however you can find both the solid dome and DSC figures on Trilogo cards.
FWIW I don't consider the DSC miscard or the Meccano Trilogo solid dome R2 as part of a "first 12" Trilogo set but then again I find the whole idea of a first 12 Trilogo set rather ridiculous anyway :lol: :roll:
Safer to stick to the 1st 12 backs !! , I would mix up Palitoy and Kenner. A lot of people have tried the Palitoy route and unfortunately did not complete
The other problem with the first 12 characters on trilogos is that several of them are bloody difficult to find. Although not particularly rare, Luke Han and Leia very rarely come up for sale as they are so desirable, so if you are impatient you could easily spend double the amount Joe's price guide lists them for. Vader is probably the easiest and cheapest to find, followed by Ben.
Also, not sure if everyone would agree but IMO several of the first 12 characters are harder to find on a trilogo card than any other (excluding rare foreign cards of course.) Luke, Leia, and Jawa are definitely more scarce on trilogo cards than any other. If budget is putting you off 12 backs, you may be better off trying to do an ESB or ROTJ Kenner run. I tried to do a ROTJ run a few years ago but Leia is very expensive these days.