I understand why everyone wants to use the PPP ratio, but sometimes it just doesn't fully reflect accurately what you are getting with some of these larger sets.
(According to the weights on bricklink)
75192 Millennium falcon: 13150 grams / 28.99 lbs = $27.60 per lb of plastic
75252 Imperial Star Destroyer: 12480 grams / 27.51 lbs = $25.45 per lb of plastic
75313 AT-AT: 10708 grams / 23.61 lbs = $33.88 per lb of plastic
75309 Republic Gunship: 5620 grams / 12.39 lbs = $28.25 per lb of plastic
I do find it interesting though that the AT-AT comes out to a good chunk higher price for the amount of material you get in the set. We all know there is the huge Disney/Star Wars tax, but I do agree that the AT-AT does appear to be unnecessarily expensive. I think that at the price of $700 it would be a bit more of a reasonable deal. That said, I did buy the set, and it's a beautifully big set as well, but I can understand why the idea of it being too expensive comes from.
Sure, if you want to factor in inflation from 2017 the Millennium falcon would cost roughly $907 in todays rates. Which roughly equals out too $31.29 per lb of plastic. In all honesty, in those terms, the AT-AT really isn't that bad of deal. (obviously this is all subjective and everyone's value of worth is completely different.)
But this puts it a little better in perspective about where Lego is coming up with the prices, and in all honestly, isn't super out of the line for them and still within reason for the other massive UCS sets that Lego has released recently.
For comparison of other big sets:
10276 Colosseum: 10780 grams / 23.76 lbs = $23.15 per lb of plastic
10294 Titanic: 14000 grams / 30.86 lbs = $20.41 per lb of plastic