The Nacecare DP420 is a fine machine and covers a lot of ground efficiently.
However, I disagree that vapor steam cleaning is a waste of time, especially in a residential setting. I use 400F vapor to do grout lines and believe me, it works. Since the pressure is relatively low, there is no impact damage to grout. Since the water flow is negligible, there is almost no injection under the tile and since the temperature is ridiculous, the grout is flushed deeply into the porous
matrix.
Slops recovery is complete with a squeegee/steam head. Edging is easy with a steam vacuum crevice tool attached.
Perfection is not promised and seldom attained. Production can be limited, but it is of superb quality. The floor is about as close to clean as can be done and some people will pay for that.
I like people who pay for that..