The distinction that matters is permit status, not finish quality. The City of Saskatoon inspects a secondary suite for egress windows, ceiling height, a separate entrance in many cases, and fire separation. A beautifully finished basement built without that permit still fails a lender's or appraiser's test for legal secondary income.
Development quality is the second lever once legality is settled. An appraiser lists a permitted secondary suite's floor area separately from the main living space and applies a lower rate to it than to above-grade square footage, then adjusts further for a full bathroom, proper insulation and a working, separate heat supply, which is why two basements with the same square footage can land at different figures. A buyer's own home inspection, typically $400 to $600, will usually catch a missing heat source or an undersized window before financing closes.
Public records and online estimates generally see the finished square footage but miss whether the work was permitted, which is exactly the gap that produces a low number for a seller who did everything correctly. Get your hand-reviewed valuation from Joel Dyck.