I believe the most common double recessive is Albino Pied (especially if you count the normal Albino Pied combination and the Dreamcicle, Lavender Albino and Pied). The 2 cheapest double recessive projects that I have seen are Caramel Glow (Caramel Albino and Hypomelanistic) and True Ghost (Hypomelanistic and Axanthic). I have also seen that Snow (Albino and Axanthic) have not cost too much. I think that Albino Pied and Hypomelanistic Pied are the two more common double recessive projects that I have seen on the more expensive side. I think that is because of what you said, that while some big breeders are working with these 2 projects, they are visually stunning.