One way to make infill pencil out

Let's Infill A Traditional Neighborhood (And Make A Profit)

It is, in general, cheaper to build on open land than to attempt to build infill in an existing neighborhood.  Can you build infill in a reasonable way, and have it pencil out?  Over at Strong Towns, they provide some examples of how to turn an underutilized block into a quality mixed use development, and have it pencil out. 

It seems that creating lovable, fine-grained, human-scale places can be profitable - even around a very expensive city like New York City.
— Andrew Price, Strong Towns