Yeah honestly, I really think he's not overpriced given that: his entire body is a completely a new sculpt; he has an intricate robot body that requires a lot of care/attention with the engineering (just as much if not more than any IM suit); he's 16 inches tall; he's the Avengers baddie of the second film
Now, I know folks have said that the head sculpt is inaccurate when compared to the Empire magazine cover, but upon closer inspection I think that might not be true after all. When I was comparing various images of Ultron Prime, I noticed that the Empire cover seems to have added more panel lines on his face. If you compare screenshots of Ultron Prime's face from the trailers, the lines on HT's sculpt seem to match the onscreen look pretty damn closely. Aside from the obvious fact that the Empire cover has him scowling (hence the major difference in expression), it really does seem like a different model from the one we've been seeing in the trailers.
At this point I do ought to wonder, was the Empire cover an earlier concept design for Ultron Prime? Because HT's sculpt seems to match the various shots of Ultron Prime from the trailers, e.g. the "nasal" ridges on the sides are thicker and much more prominent, the panel lines underneath his "cheekbones" (the one just above the edges of his "mouth") are farther down unlike the Empire cover
Honestly I think the biggest problem that HT is having a hard time dealing with is the fact that, while it's easy to smooth out the panel lines on a full 3D CGI model, they need thin them out on a figure. I think what makes the sculpt look more "busy" than it should is the fact that the lines on his face need to be thinner, especially since some of them are nearly invisible in the shots that we've seen of Ultron Prime.
Yes, all the lines on HT's sculpt are definitely accurate in terms of their placement/inclusion, rather they should be less prominent and should look more like small engravings on the actual sculpt. That said, the head sculpt definitely looks when going by the convention photos, especially since the light reflecting off the sculpt seems to obscure those sculptural lines and streamlines the overall sculpt to create a more smooth appearance.