<15 miles from city center.

In my city, which is probably similar to yours, with not very high population density, no more than  20 such undeveloped plots (farm land with or without houses) that satisfy the above criteria.  But I am not familiar with developer's line of work.

5-10 acres can have a value to be developed into small apartment complex/commerical properties, if the location is good. Every day I pass a plot of 23 acres. It has a sign for sale for 10 years and finally it is being developed... good location.