Yes, but blame Skylanders for starting the whole craze. And the other Lego games all launched at $50-60, so it's not fair to compare the discounted $20-40 to the full price of Dimensions. And even then, Dimensions comes with hardware and minifigures, even if they're not rare figures (Gandalf, Batman, and Wyldstyle aren't hard to get from small sets).
And the expansions are more like bite-sized versions of the other games. For example, Portal would have Portal mechanics, Doctor Who has Doctor Who mechanics.
Add to that, the minifigures. Cyborg's previous cheapest set was the Darkseid set. It's much cheaper to buy the playsets than the full sets, if you only care about the minifigure. Then there's the new ones, like Wizard of Oz, Chell, Slimer, Staypuft, Twelfth Doctor, K-9, Cybermen, Dalek...
But yes, it will cost like $450 to buy everything with GCU, if you don't wait for a sale. It's definitely a lot of money -- around what all of Trap Team cost. That's why I only ordered the sets that have unique figures with GCU (Chell and Wizard of Oz, as Best Buy doesn't have any Doctor Who ones listed yet).