Cost of adding Master suite to 2/1

[Neal Kay]

been analyzing a house and want some opinions on adding a master suite to a 2/1. The house is 1427 sq ft for sale by owner at $203k, renovated 3/2s in the neighborhood are averaging $230 a sq ft so adding a 365sq ft master suite would bring the ARV to $410k. From those with experience adding a master suite of this size, what was your cost?