Hi MTR,
Depending on the location (zoning, amenity, facilities,etc), marketability and budgets/feasibility, and the site dimensions, you might consider basement carparking. Placing carparking facilities below ground will add additional apartments on the ground. Also having carparking away from public and visitor sight, and having a residential interface on all sides at ground level, is a better urban design solution which adds value to the overall development. However, you've got to do the maths to see if the higher costs is offset by higher yield and sales.
I'd allow costings FROM $2200/sqm if you're going retail.