The distinction between advertised and completed rents is the key missing piece. If S$7,133 is only an asking figure, I would lean toward a modest adjustment and early, non-confrontational conversation. If the tenant declines, Amir can then compare the likely vacancy and preparation costs with...
A sensible next step is a comparison grid: completed sale date, distance, floor area, usable bedroom layout, condition, parking, outdoor space and recurring charges. Keep the three asking comparables as context, not proof of achieved value.
For the property-tax concern, get the parcel-specific...