Is JD your friend?
Each house is different and this one has quite a few around it. I would be surprised if it sells for 1.6m.
I dont expect it to reach 1.6m, but it's not exactly common to place an 18x18 with no houses around it.
The cost is what it is due to having to purchase other homes e.g. small plots in order to demolish them and place a larger house.
You can't just run through the woods and place an 18x18.
For reference.. an 18x18 fell last night and 4 seperate small plots were placed in its spot. Those plots sell for 2-400k each simply because they're blocking a potential 18x18 placement.
4 plots at 250k/ea plus the 250k+ to place a large plot.. cost to simply place an 18x18 is nearly 1m on the low end.