Gk104 is 294mm^2, Tahiti is 352mm^2, Gk110 is 551mm^2. I would consider Tahiti to be equal level of GK104, they're almost identical die size (you could also say the difference is due to 384 vs 256 bit bus).
GK104 is equally as "high end" as Tahiti, GK110 is not even close to being a Tahiti competitor.