The Graphitti books are well worth the investment IMO, although it depends on where you live (the shipping to the Netherlands was very expensive).
The books you bought have been collected in the Graphitti HC's number 4 & 5. HC's number 8 & 9 collect the earlier Blueberry storylines. #8 Collects the entire "Iron Horse" storyline and #9 collects the aforementioned "Lost Dutchman's Mine" / "Ghost with the Golden Bullets" storyline together with Jim Cutlass (from Epic Moebius #8).
Oh and enjoy reading Blueberry for the first time