Bearing in mind these cost factors, the average cost of a professionally-installed lawn irrigation system is $500-$1,000 per zone, or around $2,500 to $5,000 for a typical ½ acre lot. Note, however, that zones are, proportional to the entire system cost, cheaper to install.This means that sprinkler system installation on a 4,000 sq. ft. lawn, for example, isn’t necessary twice as expensive as on a 2,000 sq. ft. lawn.ote, however, that zones are, proportional to the entire system cost, cheaper to install. This means that sprinkler system installation on a 4,000 sq. ft. lawn, for example, isn’t necessary twice as expensive as on a 2,000 sq. ft. lawn.