lets see... sky cap is 255 blocks
avg. surface is 65 blocks
So we have 190 blocks in height.
I'm assuming it's square, at a width and depth of 12×12.
Lets be generous and say that a third of its surface is glass.
12×12×190= 27360 blocks
9120 glass panes.
Every 4 blocks there's one floor. 12x12 cobblestone except for the bottom floor, which does not have hand-laid floor.
(190 / 4 - 1) * 144 = 6696 blocks of cobble for the floors
Two ladders going from bottom floor to roof would end with 190×2 ladders. multiply by 6 for sticks, divide by 2 for planks, by 4 again for logs. Brings us at 285 logs.
perhaps far-fetched, but meh. 46 floors, 2 torches per floor.
This brings the total of blocks to:
cobble: 24936 blocks == 389,625 stacks == 7,3 DCs
glass: 9120 blocks == 142,5 stacks == 2.64 DCs
logs: 285 blocks == 4.5 stacks
Lets be generous and say one DC of cobble is worth 10 iron.
Glass will be worth a bit more because of the double costs of sand and fuel. I'd say up to 35 iron per DC.
Logs being renewable only have little value. 0.5 iron per stack seems fair to me
73 iron for the cobble, 93 for the glass, 2.5 for the logs. Totaling 168,5 iron.
With your own conversion rate, this would translate to just over 5 diamonds.
the blocks mined will at least have cost you 15 pickaxes, which would end up being the most expensive part, at 3 diamonds a piece.
your total: -40 diamonds.
Plus the fact that the building is ugly and doesn't fit in the environment. 12x12 is too slim for a building that is 190 tall. Cheap materials don't add any value, and location is not specified.
If I were you, I'd take any offer I'd get and leave.