The comparable selection is where most of the accuracy lives. Three to five genuinely similar sales beat a dozen loose ones, and each is adjusted up or down for the differences that a buyer would actually pay for: lot width, garage, basement development, age of mechanical systems, and outlook. Listings that never sold are evidence of what the market refused, not of what it pays.
The walkthrough supplies the inputs no database holds. Age and condition of furnace, shingles, windows and hot water tank, the quality of a basement development, whether a suite is permitted with the City of Saskatoon, and whether an addition or a deck went up under permit all move the number materially. Where the file and the house disagree, the house wins.
The output is a range, not a single figure, plus the net. Seller closing costs generally run 4 to 6 percent of the sale price with legal fees of $800 to $1,500 inside that, so you see what you keep, not just what you list at. The reason it is hand-reviewed is that online estimates and public records cannot see renovations done without a permit, and those are precisely the improvements a seller loses money on when nobody counts them.