How much does it cost per square foot to have grass seed installed?

firstly you have to find out what kind of seed you have,domestic lawn seed,or expensive Golf course fescues and creeping brown bents,which are so small you can bearly see them.

domestic could be 40 or 60 grams per sq ft

golf course could be 8 grams per sq ft,because there would be millions of seeds in 8 grams compared to domestic grass with a couple of thousand.