If you had a new construction experience you will have more reality on this topic but it has many other implications useful for those who never had one.
With a new house or after a big renovation windows are not only extra dirty, they have unusual particles/dirt on them that can’t be cleaned off with regular window cleaning methods which would be the hand wash, or the water fed pole wash.
Silicone, paint, manufacturer’s labels, plaster are just a few to name of the particles one can find on the glass. And these all need up close access, which becomes interesting when you have a trellis in your way or other structural or design obstacles.
The usual and normal approach for post construction window washing was using the scraper blade. That took care of pretty much everything, save for silicone or other “gluey” substances. But that has become problematic of late with the “advent” of glass manufacturers’ drop of air quality around their furnaces.
Dust particles are now generally allowed to get “baked” on to the glass’ surface, and being microscopic in size they are invisible to the naked eye. The application of blade scraper on such window surfaces will dislodge these fine particles and by pushing them along the glass surface these particles will create comet like, fine scratches.
Hence before even beginning such window cleaning job one must test the glass during the estimating phase to see what quality windows they are dealing with. I can safely state that almost every single heat treated (tempered) glass suffers from this defect.
That leaves the professional window cleaner with a problem. But long story short, at the end of it all one have to apply a lot more elbow grease in lieu of the good old blade scraper.
And the result is significantly increased post construction window cleaning prices which by other, not so professional or behind the times, cleaners can generously be ignored.
So the saying remains true: there will always be someone who does is cheaper!
The question for you is: do you think it’s worth the savings?