The average price per acre was Sh1.2 million in 2011, but is more than Sh120 million today.
The man was hacked to death on Friday at dawn after refusing demands by raiders.
The houses are selling off-plan for between Sh9.25m and Sh10.5m.
The ambitious project is expected to greatly raise the profile of Machakos County.
Most Kenyans acquiring houses are not doing so for speculative intentions.
The 0.5% levy is payable to the authority by owners of projects above Sh5 million.
The property is expected to appeal to high net worth international buyers.
Phase one and two of the project, comprising 850 housing units are completed and fully sold.
Nairobi building permit fees are said to be the highest across the continent.
The factory has a capacity to produce 126,720 expanded polystyrene panels (EPS) panels a year.