to DA or Build

our family owns a 11 level building in the cbd, it on over 2000m2 the land value is around $28,mil

we are thinking about designing a 270meter 80 level mixed uses ( retail,commercial, hotel and res)

then having BCC approval the DA and then selling the property.

does any know know of current rate of

1 m2 build cost of mixed used large scan high-rise?

2 m2 sale price of a project once finished

3 m2 sale price of project once da approved