The price would come down if mandated for all rental units, but it’s still going to be a semi-skilled laborer with specialty equipment (and now, a government mandate) for 2 hours minimum, plus all the office, administrative, and bureaucratic overhead associated. That’s not going to be much less than $500 in any case and if you have asbestos pipe insulation, lead painted windows, or other spreadable hazards, you may not be able to test. If you have a fireplace/pellet stove/other solid fuel appliances, you have to have all appliances and ashes cold, meaning some appointments are going to be busts. Other combustion appliances need a shutdown before and startup check after the test.
In just the US, this could be over 100K jobs dedicated to just this task, or 200K if needed for all owner-occupied housing every year (rather than just upon transfer). Whether that’s a good or bad thing depends on your point of view, but I don’t see a likely benefit commensurate with burning that many people on just this task.
For a compareable result an analysis of the wall and roof structure (structure and surface area) and the corresponsing transmission factors has to be done.